Rigid substrate, preparation method thereof and application of rigid substrate in atomic oxygen prevention

Abstract

The invention relates to a rigid substrate, a preparation method thereof and application of the rigid substrate in atomic oxygen prevention. The rigid substrate structurally comprises a first polyimide insulating film, a first panel, a light high-strength core material with a honeycomb structure, a second panel and a second polyimide insulating film in sequence from top to bottom; through holes distributed in an array mode are formed in the surface of the second polyimide insulating film.

Description

Technical Field

[0001] The present invention relates to a rigid substrate, a preparation method thereof, and an application in anti-atomic oxygen, belonging to the technical field of aerospace materials and applications. Background Art

[0002] The solar cell wing is the only energy source for many on-orbit spacecrafts and an important component of the spacecraft. The substrate of the spacecraft solar cell wing is usually composed of parts such as a polyimide film and a reinforcing panel, on which solar cells are pasted. It is a key component of the solar cell wing, used to support the battery circuit and provide power for the on-orbit operation of the spacecraft, playing a crucial role in the normal operation of the spacecraft.

[0003] At present, solar wing substrates mainly include rigid substrates, semi-rigid substrates, and flexible substrates. Rigid substrates are a commonly used and very important type of solar wing substrate and are the most widely used at the present stage. The rigid solar wing substrate adopts a composite sandwich structure form. Generally, the face sheet can be made of glass fiber composite material, aluminum alloy, carbon fiber composite material, and Kevlar fiber composite material. Currently, the carbon fiber composite material grid-like face sheet is the most widely used. The sandwich mostly uses an aluminum honeycomb core. The upper and lower carbon fiber composite material face sheets are respectively pasted on both sides of the aluminum honeycomb core through an adhesive film. On the front side (the side where the battery is pasted) of the substrate, a layer of polyimide film (Kapton-type polyimide) is pasted as an insulating layer to isolate the solar cell circuit from the substrate structure. In addition, the aluminum honeycomb core is generally protected by a carbon fiber composite material frame around it. However, there are a large number of highly reactive atomic oxygen (AO) in the near-earth space environment, which will cause strong oxidation and erosion of the surface materials (carbon fiber / epoxy composite material, polyimide film) of the rigid substrate of the spacecraft exposed to the space environment for a long time, resulting in serious mass loss and performance degradation, which can directly lead to component failure and affect the on-orbit service life of the spacecraft. With the application and development of low-orbit long-life spacecrafts in China, the surface materials of the rigid substrates of long-life low-orbit spacecrafts exposed to the space environment must be protected against atomic oxygen. Summary of the Invention

[0004] For this reason, the present invention provides a rigid substrate, a preparation method thereof, and an application in anti-atomic oxygen.

[0005] On the one hand, the present invention provides a rigid substrate. The structure of the rigid substrate from top to bottom sequentially includes: a first polyimide insulating film, a first face sheet, a lightweight and high-strength core material with a honeycomb structure, a second face sheet, and a second polyimide insulating film; through holes (vent holes) are arranged in an array on the surface of the second polyimide insulating film. Therefore, compared with the single-sided insulating film of a common rigid substrate, polyimide films are pasted on both the upper and lower surfaces of the rigid substrate in the present invention, and through holes are arranged in an array on the surface of the second polyimide insulating film.

[0006] Preferably, the lightweight and high-strength core material with a honeycomb structure is an aluminum honeycomb or an aramid honeycomb core, with a thickness of 5 to 80 mm, preferably 10 to 40 mm; the holes in the honeycomb structure are hexagonal columnar hole structures, and the circumscribed circle diameter of the hexagonal columnar holes is 2 mm to 50 mm, preferably 3 mm to 30 mm.

[0007] Preferably, the first panel is a grid-like panel made of a carbon fiber / resin composite material, a glass fiber / resin composite material, or a Kevlar fiber / resin composite material; the second panel is a grid-like panel made of a carbon fiber / resin composite material, a glass fiber / resin composite material, or a Kevlar fiber / resin composite material.

[0008] Preferably, the thickness of the first panel and the second panel is 0.02 to 2 mm; the resin is a thermosetting resin, preferably at least one of epoxy resin and cyanate ester.

[0009] Preferably, the thickness of the first polyimide insulating film and the second polyimide insulating film is 5 to 200 μm, preferably 12.5 μm to 125 μm.

[0010] Preferably, the diameter or side length of the through holes in the second polyimide insulating film is 0.1 mm (100 μm) to 20 mm; the area ratio of the through holes in the second polyimide insulating film is 0.005% to 1%; preferably, the shape of the through holes is square or circular.

[0011] Preferably, a first atomic oxygen protection layer is provided on the surface (upper surface or / and lower surface) of the first polyimide insulating film; a second atomic oxygen protection layer is provided on the surface (upper surface or / and lower surface) of the second polyimide insulating film and the inner surface of the through holes.

[0012] Preferably, the first atomic oxygen protection layer and the second atomic oxygen protection layer are composed of an organic / inorganic composite structure containing Si groups; the average content of Si in the first atomic oxygen protection layer and the second atomic oxygen protection layer is 2 to 20 at%, and the Si content gradually decreases from the surface to the inside; the thickness of the first atomic oxygen protection layer and the second atomic oxygen protection layer is 0.1 μm to 50 μm.

[0013] Preferably, a bonding layer is provided between the first panel and the second panel and the lightweight and high-strength core material with a honeycomb structure; a bonding layer is provided between the first polyimide insulating film and the first panel; a bonding layer is provided between the second panel and the second polyimide insulating film; the components of the bonding layer are at least one of epoxy resin, cyanate ester, and silicone resin.

[0014] Preferably, the rigid substrate further includes a carbon fiber / epoxy resin frame.

[0015] On the other hand, the present invention provides a method for preparing a rigid substrate, comprising: (1) Adhering a first panel and a second panel to the upper and lower surfaces of a lightweight and high-strength core material having a honeycomb structure; (2) Bonding a first polyimide insulating film and a second polyimide insulating film to the surfaces of the first panel and the second panel respectively; (3) Making holes on the surface of the second polyimide insulating film to obtain the rigid substrate.

[0016] Preferably, a first atomic oxygen protection layer and a second atomic oxygen protection layer are prepared on the surface of the obtained rigid substrate, and the preparation method comprises: performing activation treatment, silicone modification treatment, and stabilization treatment on the surface of the first polyimide insulating film, the surface of the second polyimide insulating film, and inside the through holes.

[0017] Preferably, the activation treatment includes ultraviolet irradiation treatment, wet chemical method treatment, plasma treatment, and corona treatment.

[0018] Preferably, the silicone precursors used in the silicone modification treatment include one or more of halogenated silane-based silicones, alkoxysilane-based silicones, aminosilane-based silicones, acyloxysilane-based silicones, and silanol-based silicones, preferably one or more of halogenated silane-based silicones, alkoxysilane-based silicones, and aminosilane-based silicones, and more preferably aminosilane-based silicones.

[0019] Preferably, the stabilization treatment includes one of ultraviolet photooxidation treatment, oxygen plasma treatment, or ozone oxidation treatment and a subsequent heat treatment process to reduce stress.

[0020] Preferably, after the first panel and the second panel are co-cured with the first polyimide insulating film and the second polyimide insulating film respectively, they are adhesively cured into an integral body with the lightweight and high-strength core material having a honeycomb structure and the carbon fiber / epoxy resin frame by using a high-temperature process; preferably, the temperature range of the high-temperature process is 60-200°C, and the atmosphere can be vacuum (<10 Pa), air atmosphere, or inert atmosphere; Alternatively, after the first panel and the second panel are cured with the lightweight and high-strength core material having a honeycomb structure and the carbon fiber / epoxy resin frame, the first polyimide insulating film and the second polyimide film are adhered to both sides; preferably, the curing temperature is 60-200°C, and the atmosphere can be vacuum (<10 Pa), air atmosphere, or inert atmosphere; Alternatively, the first polyimide film, the first panel, the second polyimide film, the second panel, the lightweight and high-strength core material having a honeycomb structure, and the carbon fiber / epoxy resin frame are integrally cured and formed; preferably, the temperature for the integral curing and forming is 60-200°C, and the atmosphere can be vacuum (<10 Pa), air atmosphere, or inert atmosphere.

[0021] On the other hand, the present invention provides an application of a rigid substrate in preventing atomic oxygen (in the field of low-earth orbit space environment).

[0022] Beneficial effects: In the present invention, the design of the rigid substrate does not affect the function of the original rigid substrate in the space environment on the one hand, and is conducive to better carrying out atomic oxygen protection on the rigid substrate on the other hand. It can have excellent atomic oxygen resistance performance, and the atomic oxygen protection surface modification film layer on the surface takes into account excellent atomic oxygen resistance performance, coating firmness and thermal cycle resistance performance, does not affect the mechanical properties of the original rigid substrate, meets the vacuum outgassing performance, and solves the problems of service life and reliability caused by atomic oxygen erosion during the application of the original rigid substrate in the low-earth orbit environment. In addition, the rigid substrate designed in the present invention has a different structure from the original rigid substrate, but does not change the original vacuum bag oven curing process of the rigid substrate, does not change the types of raw materials to be purchased, and can still be mass-produced in batches using the original rigid substrate production line. At the same time, the atomic oxygen modification method of the present invention theoretically has no raw materials restricting its large-scale production, the solution can be stored for a long time, the required equipment can be purchased or developed, and there are no factors restricting its large-scale production, which is conducive to obtaining actual batch applications. Description of the drawings

[0023] Figure 1 It is a schematic structural diagram of the front side (battery-attached side) of a rigid substrate with a conventional single-sided polyimide film and the carbon fiber / epoxy resin composite grid panel and aluminum honeycomb sandwich on the back side; Figure 2 It is a front view (battery-attached side) of the solar wing substrate with double-sided polyimide films in the present invention and an opening diagram of the polyimide film surface on the back side; Figure 3 It is the appearance diagram of the rigid substrate in Example 1 after the thermal vacuum test. The substrate appearance is flat, without phenomena such as bubbling, and meets the outgassing requirements; Figure 4 It is a scanning electron microscope image of the surface morphology of the atomic oxygen protection layer on the outer surface of the rigid substrate in Example 1 after the thermal vacuum test. The surface of the atomic oxygen protection layer is flat and has no obvious defects such as cracks; Figure 5 It is a physical diagram of the carbon fiber / epoxy resin composite grid panel surface of the conventional rigid substrate in Comparative Example 1; Figure 6 It is a physical diagram of the carbon fiber / epoxy resin composite grid panel surface of the conventional rigid substrate in Comparative Example 1 after being irradiated by AO. Compared with Figure 5 the surface carbon fiber / epoxy resin composite grid panel is almost completely eroded, and most of the polyimide on the inner side of the honeycomb (the inner side polyimide is protected against atomic oxygen, and only the battery-attached side is protected against atomic oxygen) is also eroded; Figure 7It is a physical diagram of the double-sided polyimide film rigid substrate obtained in Example 1 after the AO test. Detailed implementation manners

[0024] The present invention will be further described through the following implementation manners. It should be understood that the following implementation manners are only used to illustrate the present invention, rather than limiting the present invention.

[0025] In the present disclosure, the rigid substrate is a multi-layer structure, including: from the side attached to the battery to the other side, in sequence, an atomic oxygen protection layer (the first atomic oxygen protection layer), a polyimide film (the first polyimide insulating film), an adhesive film (bonding layer), a carbon fiber / epoxy resin composite material grid panel, an adhesive film (bonding layer), an aluminum honeycomb sandwich, a carbon fiber / epoxy resin composite material grid panel, an adhesive film (bonding layer), a polyimide film with air holes (the second polyimide insulating film), and an atomic oxygen protection layer (the second atomic oxygen protection layer). In the present invention, compared with a common substrate, a polyimide film is adhered to the back, and the polyimide film on the back has openings (through holes) for gas release inside the substrate.

[0026] In an optional implementation manner, the first / second panel is composed of a carbon fiber / resin composite material grid-like panel. Among them, for large-area solar wings that require high stiffness and low weight, high-modulus carbon fibers are generally used for carbon fibers, and thermosetting resins such as epoxy resins or cyanate materials are used for resins. Reinforcing layers with different directions and thicknesses can be set at appropriate positions on the panel as needed to meet the requirements for stiffness and strength in different regions.

[0027] In an optional implementation manner, the thickness of the aluminum honeycomb core is 10 - 40 mm. The side walls of the aluminum honeycomb have needle-shaped holes communicating for gas release to adapt to the vacuum conditions of the space environment and prevent the honeycomb cells from being damaged by internal pressure in the space environment, thus damaging the entire substrate structure. In order to reduce weight, honeycomb materials with a thin thickness and large cell sizes are preferably used as much as possible. In the parts of the substrate that need to be strengthened, honeycombs with smaller cells can be used while ensuring the gas release rate. The thickness of the polyimide insulating film is 12.5 - 125 μm.

[0028] In an optional implementation manner, for the polyimide air holes on the back, on the one hand, the number should be minimized as much as possible to reduce the difficulty of implementing atomic oxygen protection at the opening positions. On the other hand, the air holes should have a certain area and number, and the arrangement and distribution mode of the air holes should be considered to ensure the gas release rate of the solar wing substrate from the air environment to the vacuum environment and prevent the honeycomb cells from being damaged by internal pressure in the vacuum environment, thus damaging the entire substrate structure. When the gas release rate requirement is met, reducing the number of holes is beneficial to improving the implementation speed of preparing the atomic oxygen protection layer inside the holes and reducing the reliability hidden dangers caused by limited detection inside the holes. Therefore, for the opening area and specific number setting of the holes, it is advisable to be as small as possible while meeting the gas release rate requirement during the on-orbit application of the rigid substrate. The requirement for the gas release rate is determined by the specific application situation of the spacecraft.

[0029] In an alternative embodiment, the vent holes should be opened along the inner side of the carbon fiber / resin grid. On the one hand, the bonding area between the polyimide film and the grid-shaped panel of the carbon fiber / resin composite material should be reduced as little as possible due to the opening, ensuring good mechanical strength. On the other hand, the size of the carbon fiber / resin composite material grid should be fully utilized to ensure a relatively fast gas release rate. At the same time, the larger holes are conducive to the implementation of the subsequent inner hole atomic oxygen protection process.

[0030] In an alternative embodiment, the atomic oxygen protection layer can be prepared on one side or both sides of the surfaces of the two polyimide insulating films. The inner side of the holes exposed at the openings of the back polyimide also has an atomic oxygen protection layer.

[0031] In an alternative embodiment, whether to prepare an atomic oxygen protection layer on the surface of the polyimide insulating film on the battery cell attaching side can be determined according to the atomic oxygen protection performance of the adhesive used on the battery cell attaching side, the bonding strength between this atomic oxygen protection layer and the adhesive for attaching the battery cell, and the usage requirements. Usually, after preparing an atomic oxygen protection layer based on the Si system, the bonding strength with silica gel is better. It is preferably to prepare an atomic oxygen protection layer on the surface of the polyimide insulating film on the battery cell attaching side.

[0032] In an alternative embodiment, the rigid substrate includes a carbon fiber / resin frame to protect the edge part of the aluminum honeycomb core. Whether to prepare an atomic oxygen protection layer on the carbon fiber / resin frame can be determined according to the thickness of the carbon fiber / resin frame and the usage requirements. Preferably, an atomic oxygen protection layer should be prepared on the outer surface of the carbon fiber / resin frame.

[0033] In an alternative embodiment, the atomic oxygen protection layer is composed of an organic-inorganic composite structure containing Si groups, and the Si content gradually decreases from the surface to the interior of the substrate, with a thickness of 0.1 - 50 μm.

[0034] In the embodiments of the present invention, a method for preparing a rigid substrate is also provided. The rigid substrate can be formed by using the vacuum hot pressing process commonly used in aerospace, that is, the vacuum bag oven curing process. Preferably, the vent holes (through holes) are opened according to the usage situation after the overall curing of the rigid substrate, and the atomic oxygen protection layer is prepared after the rigid substrate is developed, without changing the original process flow of the rigid substrate. The preparation of the atomic oxygen protection layer on its surface is easier to implement than that on the surface of a conventional rigid substrate with a single-sided polyimide insulating film (where the polyimide in the complex honeycomb structure of the carbon fiber / resin grid and the aluminum honeycomb sandwich is exposed to the low-earth orbit atomic oxygen environment), and it is easy to prepare on a large scale.

[0035] The present invention also provides a preparation of a rigid substrate, which mainly includes the molding of a rigid substrate multilayer structure; pre-treatment such as substrate protection and cleaning; anti-atomic oxygen modification of polyimide and carbon fiber composite materials in the vent holes of the substrate; carbon fiber / epoxy modification of the substrate frame; polyimide modification of the substrate surface; and stabilization treatment of the substrate surface. Among them, the modification steps of different parts have a sequence. For example, considering that the implementation process of the inner hole modification process is relatively long, the operation process is easy to affect the polyimide modified film surface on the outer surface of the substrate. Generally, the inner hole modification treatment should be carried out first, and then the polyimide treatment on the outer surface of the substrate should be carried out. In the present invention, atomic oxygen protection is achieved by an organic-inorganic hybrid silicon film layer containing a silicon source, and the atomic oxygen-inert adhesive silicon oxide generated on the outer surface of the organic-inorganic hybrid silicon film layer under stabilization treatment or atomic oxygen environment has atomic oxygen protection performance. The precursor formula of different parts can be selected according to the characteristics of the substrate, and the stabilization treatment is carried out together after all the modification treatment steps are completed. The following is an exemplary description of the preparation process of a rigid substrate.

[0036] Forming of a multilayer structure of a rigid substrate. The multilayer structure of a rigid substrate is formed as a whole by using a vacuum bag oven curing process. The forming process sequence can be to use a carbon fiber mesh panel and a polyimide film to co-cure at high temperature, and then use a vacuum high temperature process to glue and cure the honeycomb core and the carbon fiber / epoxy resin frame into a whole. Alternatively, the carbon fiber mesh panel, the honeycomb core and the carbon fiber / epoxy resin frame are first cured and then the polyimide film is bonded on both sides. Alternatively, the polyimide film, the carbon fiber mesh panel, the honeycomb core and the carbon fiber / epoxy resin frame are integrally cured and formed. The carbon fiber mesh panel layer itself is formed by winding.

[0037] Opening holes for venting. Use a surgical blade or the like to open holes along the inner side of the carbon fiber / resin mesh. Usually, the inner size of the carbon fiber mesh with a general degree of density is about 4mm×4mm. The holes should be opened as far as possible away from the mechanically enhanced mesh density enhancement position to avoid affecting its mechanical strength.

[0038] Pretreatment such as substrate protection and cleaning. The substrate serves as a support structure, and batteries, diodes, etc. will be arranged later. For parts that may be affected by subsequent processing after atomic oxygen protection, polyimide high-temperature resistant tape can be used to protect the parts that do not need to be treated; usually, the anti-atomic oxygen surface modification layer has good adhesion to silicone rubber, etc., and no special protection treatment is required. To prevent the impact of soaking and cleaning on the substrate structure, scrubbing and other methods are preferably used for cleaning, and scrubbing with ethanol, acetone, p-xylene, etc. is preferred. Specifically, the substrate surface can be wiped three times with a dust-free cloth dipped in p-xylene solution, ethanol solution, and acetone solution respectively; or a dust-free cloth dipped in a mixture of ethanol and acetone can be used for cleaning, and after cleaning, it can be dried naturally or in an oven. Considering the heat resistance of the substrate resin, the heat treatment temperature should generally be ≤120°C. Considering that the vent hole size of the substrate is small and it is not easy to scrub, but it is easy to be contaminated by dust or adsorbed with excess substances such as carbon fiber and epoxy during the substrate processing and transportation, for the cleaning of the vent holes in the substrate, it can be first cleaned with a vacuum cleaner and then cleaned by ultraviolet ozone (UV ozone) irradiation. In addition, for stubborn oil stains on the surface of the rigid substrate, etc., it can be cleaned by wiping with p-xylene solution combined with ultraviolet ozone (UV / O3) irradiation.

[0039] Anti-atomic oxygen modification of polyimide and carbon fiber composite materials in the substrate vent holes. An organic-inorganic hybrid silicon film layer is used to perform atomic oxygen protection treatment on the inside of the substrate vent holes. Considering that both the polyimide on the inner hole surface and the carbon fiber composite material on the surface need to be protected and it is difficult to treat them separately, a silicon source that is applicable to both polyimide and carbon fiber composite materials is used, and the wettability and bonding force of the silicon source to different substrates can be improved through activation treatment. Among them, the activation treatment can be carried out by ultraviolet irradiation, plasma, corona, and alkaline and acidic solutions such as ammonia water and amine compounds.

[0040] The silicon sources for preparing the organic-inorganic hybrid silicon film layer include: one or more of organosilicon halides, alkoxysilane organosilicons, aminosilane organosilicons, acyloxysilane organosilicons, silanols, isocyanate hydrocarbon group silanes, epoxy hydrocarbon group silanes, and cyanide hydrocarbon group silanes.

[0041] The silicon source is selected from small molecule organosilicon precursors, preferably with a molecular weight not exceeding 900, and more preferably a small molecule organosilicon precursor that simultaneously contains carbon functional groups and silicon functional groups that can react with organic materials. Further preferably, it is a combination of multiple silanes, so as to form a gradient layer through the different diffusion reaction difficulties and surface energies during the diffusion reaction process, and weaken the interfacial stress. Through subsequent heat treatment, the small molecule organosilicon precursor is further promoted to diffuse and react into the polyimide and carbon fiber composite materials to form a firm organic-inorganic hybrid silicon protection layer.

[0042] Preferably, the silicone precursor is selected from aminoalkylsilane-based silicones; preferably, the silane is selected from 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltriethoxysilane.

[0043] Preferably, the silicone precursor solution can be prepared with a variety of solvents, selected from at least one of alkane solvents, ether solvents, ketone solvents, ester solvents, alcohol solvents, and benzene and its derivative solvents. It includes one or more of ethanol, isopropanol, butanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, etc. A solvent that has a certain swelling effect on the inner hole substrate but does not affect the main properties of the inner hole substrate after volatilization is preferred. Considering that it is difficult to remove the excess reagent after treatment through other operation methods except for steps such as automatic volatilization of the reagent, it is preferred to use a pipette to quantitatively modify the reagent. On the one hand, it ensures that the polyimide and its carbon fiber composites at different height positions are protected, and on the other hand, it minimizes unnecessary reagents to reduce weight as much as possible and avoid stress problems caused by an increase in film thickness.

[0044] Anti-atomic oxygen modification of the carbon fiber / epoxy on the substrate border. The carbon fiber / epoxy on the substrate border also uses an organic-inorganic hybrid silicon film layer containing a silicon source to achieve atomic oxygen protection. The same reagent system as above can be used for activation and silicone modification treatment. Specifically, the number of functional groups connected to Si in the silicone precursor and the ratio of the organic group R to Si can be appropriately adjusted according to the thermal expansion coefficient of the carbon fiber / epoxy, etc., to form different crosslinking network densities, and an elastomer to a hard, glassy film layer can be prepared to achieve a better balance between thermal expansion coefficient matching and hardness. Considering the characteristics of the border, to avoid the influence on the surface polyimide during the process implementation, the silicone precursor solution can be appropriately hydrolyzed and polymerized to increase the viscosity to avoid the generation of flow marks, etc. At the same time, the brushing method can be used to avoid the influence on other parts during the spraying process and ensure full coverage of the solution on the border carbon fiber / epoxy.

[0045] Atomic oxygen resistance modification of the polyimide on the substrate surface. The polyimide on the outer surface of the substrate is also protected against atomic oxygen through an organic-inorganic hybrid silicon film layer containing a silicon source. The same reagent system as described above can be used for activation and organosilicon modification treatment. Specifically, the number of functional groups connected to Si in the organosilicon precursor and the ratio of the organic group R to Si can be appropriately adjusted according to the coefficient of thermal expansion of the polyimide, etc., to form different crosslinking network densities, and elastomers or even hard, glassy film layers can be prepared to achieve a better balance between the coefficient of thermal expansion matching and hardness. Considering the characteristics of large-area treatment of the surface polyimide and the high requirement for bonding strength, large-area spraying can be used to ensure complete coverage of the surface polyimide by the solution. At the same time, the silicon source of the organic-inorganic hybrid silicon film layer should be selected from small-molecule organosilicon precursors, and subsequent heat treatment is used to further promote the diffusion reaction of the small-molecule organosilicon precursors into the interior of the polyimide and carbon fiber composite material to form a firm organic-inorganic hybrid silicon protective layer.

[0046] Stabilization treatment of the substrate modification layer. Among them, the stabilization treatment of the substrate modification layer can include heat treatment, ultraviolet irradiation treatment, plasma treatment, or ozone oxidation treatment to form a SiO-like layer rich in Si and O. x The outermost surface. According to the differences in the silicon-containing gradient film layers prepared under different conditions, stabilization treatment methods such as ultraviolet photooxidation can be selected, and the stress can be reduced through further heat treatment. Among them, the UV light intensity of the ultraviolet photooxidation treatment can be 2 - 15 mW / cm 2 mW / cm 2 , and the time can be 0.5 - 24 hours. The temperature of the heat treatment can be 50 - 120 °C, and the time can be 3 - 120 hours. Preferably, the temperature of the heat treatment does not exceed 120 °C, the stabilization treatment is ultraviolet irradiation treatment, and the temperature is maintained at 15 - 120 °C, and the temperature of the secondary heat treatment is 25 - 120 °C.

[0047] The present invention also provides an application of the atomic oxygen resistance modified rigid substrate in the field of space environment. This surface-modified rigid substrate has excellent space environment tolerance in the space environment, especially in the low-orbit space environment, and also has excellent atomic oxygen resistance performance.

[0048] In a preferred embodiment of the present invention, through the atomic oxygen protection of the rigid substrate, excellent atomic oxygen resistance performance can be achieved, solving the service life and reliability problems caused by atomic oxygen erosion of the original rigid substrate in the low-orbit service environment. Moreover, the atomic oxygen resistance surface modification film layer on the polyimide surface takes into account excellent atomic oxygen resistance performance, coating firmness, and resistance to thermal cycling performance, and does not affect the mechanical properties of the original rigid substrate, meeting the vacuum outgassing performance.

[0049] The following are further examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples.

[0050] Example 1 (1) The rigid substrate has an 11-layer structure, including: from the side attached to the battery to the other side, in sequence, an atomic oxygen protection layer, a first polyimide film, an adhesive film, an M55 carbon fiber / 648 epoxy resin composite grid panel, an adhesive film, an aluminum honeycomb sandwich, an adhesive film, a carbon fiber / epoxy resin composite grid panel, an adhesive film, a second polyimide film with air vents, and an atomic oxygen protection layer. At the same time, the rigid substrate includes a carbon fiber / epoxy resin frame. The carbon fiber grid panel is formed by winding M55 carbon fiber and 648 epoxy resin, and after being co-cured at high temperature with Kapton 200HN polyimide film, it is then bonded and cured into a whole by a high-temperature process (110 °C) on both sides of the honeycomb core; (2) Use a surgical blade or the like to open holes along the inner side of the carbon fiber / epoxy resin grid (the inner size of the carbon fiber grid is about 4 mm × 4 mm). The size of the air vents is the same as the inner size of the carbon fiber grid, which is 4 mm × 4 mm. The air vents are distributed as evenly as possible, with an interval of about 100 mm, as Figure 1 shown (the area ratio of the through holes is about 0.16% of the total area of the second polyimide film before treatment); (3) Cover the side attached to the battery with a polyimide film and paste it around with polyimide tape to protect the side attached to the battery from the influence of the treatment process on the non-battery-attached side. After the protection is completed, first use a vacuum cleaner to clean the granular debris in the air vents of the substrate, then scrub it 3 times each with p-xylene, ethanol, and acetone and then dry or bake it, and finally irradiate and clean the whole substrate with ultraviolet ozone (UV / O3). At the same time, ultraviolet photooxidation can improve the surface wettability and increase the bonding force of the protection layer, making the film layer have better coating firmness; (4) Treat the polyimide and carbon fiber / epoxy resin composite materials in the air vents of the substrate with a small molecule organosilicon precursor solution. Considering that the polyimide on the inner hole surface and the carbon fiber composite material on the surface need to be protected and it is difficult to treat them separately, first, the wettability and bonding force of the silicon source to different substrates are improved by ultraviolet light activation, and then, a Si-containing atomic oxygen protection layer is prepared with a 20% N,N-dimethylformamide solution of aminopropyltriethoxysilane; (5) Treat the carbon fiber / epoxy resin composite material of the substrate frame with a small molecule organosilicon precursor solution. First, activate the surface of the substrate by ultraviolet light, and then use a solution of 20% aminopropyltriethoxysilane in N,N-dimethylformamide to prepare a Si-containing atomic oxygen protection layer by brushing method; (6) Treat the polyimide film on the surfaces of both sides of the substrate with a small molecule organosilicon precursor solution. First, activate the surface of the polyimide film by ultraviolet light, and then use a solution of 16% aminopropyltriethoxysilane and 4% aminopropylmethyldiethoxysilane in N,N-dimethylformamide to prepare a Si-containing atomic oxygen protection layer by spraying method.

[0051] After the above steps, cut a part of the sample and test the surface morphology and composition of the polyimide film on the outer surfaces of both sides of the substrate after surface modification. Observe the surface morphology with the naked eye, optical microscope and scanning electron microscope (SEM), and no cracks are found; the surface composition tested by X-ray energy spectrum (EDS) is C: 51.86 at%, O: 21.00 at%, Si: 16.01 at%, N: 11.13 at%; the thickness of the atomic oxygen protection layer combined with SEM and EDS is about 3 μm (cut the sample cross-section by ion beam, and then measure the cross-section by SEM and EDS); use the 3M610# tape sticking method, 3M2214# tape sticking method and 3M92# tape sticking method to detect that the atomic oxygen protection layer does not fall off; there are no cracks on the surface after 100 thermal cycles in the temperature range of -100 °C to +120 °C; the polyimide surfaces with atomic oxygen protection layers on both sides of the substrate have a total atomic oxygen cumulative amount of 4.08×10 22 atom / cm 2 After irradiation, there is no obvious damage, the film surface is intact, and the mass loss is about 0.17 mg / cm 2 , meeting the atomic oxygen protection technical index requirement of the application party that the mass loss ≤ 0.5 mg / cm 2 , and the atomic oxygen protection layer has excellent film layer firmness, excellent bonding force and excellent resistance to thermal cycling.

[0052] In addition, further carry out a thermal vacuum test to measure the outgassing performance and the film layer firmness of the atomic oxygen protection layer under thermal vacuum test conditions. After 3.5 cycles of thermal vacuum test in the temperature range of -95 °C to +115 °C, there is no obvious change in the substrate visually, and there are no phenomena such as bubbling; no cracks are found by observing the surface morphology with SEM, and there is no obvious change in the surface composition tested by EDS, and the Si content is 16.06 at%. The atomic oxygen protection layer has heat resistance cycling performance under vacuum conditions. From the comprehensive test results, the developed anti-atomic oxygen rigid substrate takes into account excellent anti-atomic oxygen performance, coating firmness and resistance to thermal cycling, and does not affect the mechanical properties of the original rigid substrate, meeting the vacuum outgassing performance.

[0053] Comparative Example 1 The preparation process of the rigid substrate in Comparative Example 1 was referred to that of Example 1, with the difference that: the rigid substrate had a nine-layer structure, including: from the side attached with the battery to the other side were successively an atomic oxygen protection layer, a polyimide film, an adhesive film, an M55 carbon fiber / 648 epoxy resin composite grid panel, an adhesive film, an aluminum honeycomb sandwich, an adhesive film, and a carbon fiber / epoxy resin composite grid panel, that is, a structure with a traditional single-sided polyimide film was adopted, and the polyimide film with air holes and an atomic oxygen protection layer was not pasted on the non-attached surface. The polyimide surface of the substrate with the atomic oxygen protection layer was irradiated with 3.13×10 22 atom / cm 2 . After irradiation, similar to Example 1, there was no obvious damage. Since the solar cells on the substrate surface were oriented towards the sun, the probabilities of the two sides of the substrate being in the atomic oxygen windward surface were not much different, and the atomic oxygen doses encountered were also not much different. However, after the carbon fiber / epoxy resin composite grid panel was irradiated with 3.13×10 22 atom / cm 2 , the carbon fiber / epoxy resin composite on the surface had been completely eroded, and since there was no atomic oxygen protection layer on the inner side of the holes of the polyimide film on the attached surface facing the honeycomb core, most of it was also eroded, affecting its service performance in the low-Earth orbit space environment.

Claims

1. A rigid substrate, characterized in that, The structure of the rigid substrate from top to bottom sequentially includes: a first polyimide insulating film, a first panel, a lightweight and high-strength core material with a honeycomb structure, a second panel, and a second polyimide insulating film; through holes are arranged on the surface of the second polyimide insulating film in an array distribution.

2. The rigid substrate according to claim 1, wherein The lightweight and high-strength core material with a honeycomb structure is an aluminum honeycomb core or an aramid honeycomb core, with a thickness of 5 - 80 mm, preferably 10 - 40 mm; the holes in the honeycomb structure are hexagonal columnar hole structures, and the diameter of the circumscribed circle of the hexagonal columnar holes is 2 mm - 50 mm, preferably 3 mm - 30 mm.

3. The rigid substrate according to claim 1, characterized in that, The first panel is a grid-like panel composed of a carbon fiber / resin composite material, a glass fiber / resin composite material, or a Kevlar fiber / resin composite material; the second panel is a grid-like panel composed of a carbon fiber / resin composite material, a glass fiber / resin composite material, or a Kevlar fiber / resin composite material.

4. The rigid substrate according to claim 3, characterized in that, The thickness of the first panel and the second panel is 0.02 - 2 mm; the resin is a thermosetting resin, preferably at least one of epoxy resin and cyanate ester.

5. The rigid substrate according to any one of claims 1-4, characterized in that, The thickness of the first polyimide insulating film and the second polyimide insulating film is 5 - 200 μm, preferably 12.5 μm - 125 μm.

6. The rigid substrate according to any one of claims 1-4, characterized in that, The diameter or side length of the through holes in the second polyimide insulating film is 100 μm - 20 mm; the area ratio of the through holes in the second polyimide insulating film is 0.005% - 1%; preferably, the shape of the through holes is square or circular.

7. The rigid substrate according to any one of claims 1-4, characterized in that, A first atomic oxygen protection layer is arranged on the upper surface or / and lower surface of the first polyimide insulating film; a second atomic oxygen protection layer is arranged on the upper surface or / and lower surface of the second polyimide insulating film and the surface inside the through holes.

8. The rigid substrate according to claim 7, wherein The first atomic oxygen protection layer and the second atomic oxygen protection layer are composed of an organic / inorganic composite structure containing Si groups; the average content of Si in the first atomic oxygen protection layer and the second atomic oxygen protection layer is 2 - 20 at%, and the Si content gradually decreases from the surface to the inside; the thickness of the first atomic oxygen protection layer and the second atomic oxygen protection layer is 0.1 μm - 50 μm.

9. The rigid substrate according to any one of claims 1-4, characterized in that, Adhesive layers are arranged between the first panel and the second panel and the lightweight and high-strength core material with a honeycomb structure; an adhesive layer is arranged between the first polyimide insulating film and the first panel; an adhesive layer is arranged between the second panel and the second polyimide insulating film; The components of the adhesive layer are at least one of epoxy resin, cyanate ester, and silicone resin.

10. The rigid substrate according to any one of claims 1-4, characterized in that, The rigid substrate further includes a carbon fiber / epoxy resin frame.

11. A method for preparing a rigid substrate as described in claim 1, characterized in that, Including: (1) Adhere the first panel and the second panel to the upper and lower surfaces of the lightweight and high-strength core material with a honeycomb structure; (2) Bond the first polyimide insulating film and the second polyimide insulating film to the surfaces of the first panel and the second panel respectively; (3) Open holes on the surface of the second polyimide insulating film to obtain the rigid substrate.

12. The preparation method according to claim 11, wherein, Prepare the first atomic oxygen protection layer and the second atomic oxygen protection layer on the surface of the obtained rigid substrate, and the preparation method includes: carry out activation treatment, organosilicon modification treatment, and stabilization treatment on the surface of the first polyimide insulating film, the surface of the second polyimide insulating film, and the inside of the through holes.

13. The preparation method according to claim 11, characterized in that, The activation treatment includes: ultraviolet irradiation treatment, wet chemical treatment, plasma treatment, and corona treatment.

14. The preparation method according to claim 11, characterized in that, The organosilicon precursors used in the organosilicon modification treatment include one or more of halogenated silane-based organosilicons, alkoxysilane-based organosilicons, aminosilane-based organosilicons, acyloxysilane-based organosilicons, and silanol-based organosilicons. Preferably, they are one or more of halogenated silane-based organosilicons, alkoxysilane-based organosilicons, and aminosilane-based organosilicons. More preferably, they are aminosilane-based organosilicons.

15. The preparation method according to claim 11, characterized in that, The stabilization treatment includes: a process of weakening stress by ultraviolet photooxidation treatment, oxygen plasma treatment, or ozone oxidation treatment followed by heat treatment.

16. The preparation method according to claim 11, characterized in that, After co-curing the first panel and the second panel with the first polyimide insulating film and the second polyimide insulating film (polyimide film) respectively, they are adhesively cured into a whole with a lightweight and high-strength core material having a honeycomb structure and a carbon fiber / epoxy resin frame by a high-temperature process; preferably, the temperature range of the high-temperature process is 60 - 200 °C, and the atmosphere is a vacuum, air atmosphere, or inert atmosphere. Alternatively, after curing the first panel, the second panel, the lightweight and high-strength core material having a honeycomb structure, and the carbon fiber / epoxy resin frame, the first polyimide insulating film and the second polyimide film are adhesively bonded to both sides; preferably, the curing temperature is 60 - 200 °C, and the atmosphere is a vacuum, air atmosphere, or inert atmosphere. Alternatively, the first polyimide film, the first panel, the second polyimide film, the second panel, the lightweight and high-strength core material having a honeycomb structure, and the carbon fiber / epoxy resin frame are integrally cured and formed; preferably, the temperature for the integral curing and forming is 60 - 200 °C, and the atmosphere is a vacuum, air atmosphere, or inert atmosphere.

17. Application of the rigid substrate according to claim 1 in preventing atomic oxygen.

Images