An intelligent detection method for a super-black composite film

Abstract

The present invention relates to an intelligent detection method for a super-black composite film, belonging to the technical field of film detection. The method includes the following steps: First, a multi-walled carbon nanotube color paste is sprayed on the surface of a substrate and then dried; Then, a composite ink is sprayed on the surface of the dried film to form a composite film, and the composite film is subjected to liquid nitrogen freezing treatment, freeze-drying treatment, and plasma surface treatment to obtain a super-black composite film; Electrodes are led out around the super-black composite film and connected to a voltage acquisition circuit. Two adjacent electrodes are used as the input point and output point of the exciting current, and the voltage values at the remaining electrodes are measured to obtain the voltage distribution at each electrode of the super-black composite film before damage; And the voltage distribution of the damaged super-black composite film is measured; Image reconstruction is carried out according to the voltage distribution of the super-black composite film before and after damage to obtain an imaging map of the conductivity distribution, realizing the intelligent self-monitoring and localization of local damage of the super-black composite film without introducing external sensors.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film detection, and particularly relates to an intelligent detection method for an ultra-black composite thin film. Background Art

[0002] Ultra-black materials (also known as ultra-absorbing materials) are a new type of material that can efficiently absorb incident light, with extremely high light absorption rates, and have broad application prospects in scientific research and engineering applications. For example, outside the field of view of an optical system, light such as the sun and earth-sky light (sunlight scattered by the earth's atmosphere) enters the system and reaches the detector as non-imaging light after multiple reflections, refractions, scatterings, and diffractions by internal components of the system (optical surfaces and mechanical surfaces). In addition, inside the optical system, due to the roughness, surface defects, surface contamination, etc. of the optical element surfaces, residual reflections, scatterings, and diffractions cause some of the light participating in imaging to reach the image plane of the system along abnormal paths inside the system, forming non-imaging light of optical noise. By coating the inner wall of the optical system's light shield with ultra-absorbing materials, these stray lights can be effectively suppressed, improving the detection accuracy, resolution, and detection ability of the optical system for faint targets. However, in space, there are numerous and widely distributed micrometeoroids generated by various celestial body impacts. Satellites, detectors, etc. operating in such an environment are often faced with "attacks" from micrometeoroids. Due to the large relative velocity between them and the spacecraft, a large amount of energy is generated when they collide with the spacecraft, inevitably causing damage to the optical system, especially the ultra-black materials inside the light shield, which will hinder the suppression of stray light and reduce the resolution of the optical system. In addition, due to the complex composition of space optical payloads, when imaging problems occur, the entire system needs to be checked, but the structural state of the ultra-black materials inside the light shield cannot be known in a timely manner, making the checking process more difficult. Real-time monitoring of ultra-black materials can promptly reflect the structural aging or damage that occurs under the action of external loads and internal defects, so as to discover and give early warnings in a timely manner, which can greatly reduce the maintenance time and cost and improve the self-perception ability of the overall reliability of the optical system.

[0003] To avoid damage to composite materials caused by structural detection and affect their continued use, researchers at home and abroad have developed a variety of non-destructive testing techniques for monitoring the service status of composite materials, including ultrasonic methods, radiographic testing methods, electrical sensing, etc. The ultrasonic method detects damage and defects in materials based on the differences in the reflection attenuation and resonance of ultrasonic waves in damaged and intact areas of composite materials. However, this method must know the approximate location of the damage in advance and cannot achieve real-time monitoring. The radiographic testing method uses the radiation energy that is not absorbed by high-energy electromagnetic waves after passing through the material to form an image on a photoelectric sensor for detection. Due to characteristics such as high cost and off-line detection, it is difficult to achieve on-site application. The electrical sensing method monitors according to local signal changes in the sensing network when facing external impacts, structural strains, and internal damage by installing sensors on the surface or inside of the material to form a sensing network, and has advantages such as on-line and local monitoring. However, the traditional electrical sensing method requires a large sensor network, which increases the weight and installation difficulty of the structure, and it is difficult to achieve a perfect match between the sensor itself and the composite material, which limits its application in material health monitoring. Therefore, it is urgent to develop advanced electrical sensing technology to achieve on-line real-time monitoring of composite material damage, comprehensively master the health status of the material, and ensure its reliable service in the environment. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides an intelligent detection method for a super-black composite film, which can realize the local damage intelligent self-monitoring and positioning of the super-black composite film without introducing external sensors by detecting the conductivity change of the super-black film using conductivity image reconstruction technology.

[0005] The object of the present invention is to provide an intelligent detection method for a super-black composite film, including the following steps:

[0006] S1. Spray multi-walled carbon nanotube paste on the surface of the substrate and obtain a dense film after drying;

[0007] S2. Spray composite ink on the surface of the dense film to make a composite film;

[0008] S3. Perform liquid nitrogen freezing treatment on the composite film through a self-adsorption type flat freezer, and then perform freeze-drying treatment through a freeze dryer to obtain a super-black composite film after plasma surface treatment;

[0009] S4. Lead out electrodes around the super-black composite film, and the number of electrodes on each side is 4 or 6;

[0010] S5. Connect the electrodes on the super-black composite film to a voltage acquisition circuit, use adjacent two electrodes as the input point and output point of the excitation current, measure the voltage values at the remaining electrodes, and obtain the voltage distribution at each electrode of the super-black composite film before damage;

[0011] Repeat this step for the super-black composite film after damage to obtain the voltage distribution of the super-black composite film after damage;

[0012] S6. Perform image reconstruction based on the voltage distributions of the super-black composite film before and after damage to obtain a distribution imaging map of the conductivity of the super-black composite film; realize intelligent self-monitoring and localization of local damage of the super-black composite film according to the distribution imaging map.

[0013] In one embodiment of the present invention, in S1, the process parameters of the spraying are as follows: the air pressure is 0.3 MPa - 0.5 MPa, the flow rate is 20 mL / min - 30 mL / min, the spraying distance is 200 mm - 400 mm, and the time is 10 s - 20 s;

[0014] The drying temperature is 80 °C - 100 °C, and the time is 20 min - 30 min.

[0015] In one embodiment of the present invention, in S2, the preparation of the composite ink includes the following steps: dissolve the multi-walled carbon nanotube color paste described in S1 in water and stir evenly, then continue to add a binder, a metal oxide filler, a thickener, an antifoaming agent, and an auxiliary agent and stir evenly to obtain the composite ink; the multi-walled carbon nanotube color paste is obtained by mixing multi-walled carbon nanotubes, a surface modifier, water, and an alcohol solvent.

[0016] In one embodiment of the present invention, the mass parts of each component in the composite ink are as follows: 70 - 90 parts of multi-walled carbon nanotube color paste, 5 - 15 parts of water, 1 - 5 parts of binder, 1 - 5 parts of metal oxide filler, 0.5 - 1 part of thickener, 0.5 - 1 part of antifoaming agent, and 1 - 5 parts of auxiliary agent;

[0017] The mass ratio of multi-walled carbon nanotubes, surface modifier, water, and alcohol solvent in the multi-walled carbon nanotube color paste is (5 - 10):(4 - 10):(70 - 90):(5 - 12).

[0018] In one embodiment of the present invention, the binder is selected from one or more of acrylic resin, organosilicon-modified acrylic resin, and epoxy resin;

[0019] The metal oxide filler is selected from nano-zinc oxide and / or nano-titanium dioxide;

[0020] The thickener is selected from hydroxyethyl cellulose and / or associative polyurethane thickener;

[0021] The antifoaming agent is selected from polysiloxane antifoaming agent and / or BASF Foamaster antifoaming agent;

[0022] The auxiliary agent is selected from isopropyl alcohol and / or ethylene glycol;

[0023] The surface modifier is selected from one or more of sodium diphenyl vinylbenzene disulfonate, polyvinylpyrrolidone, and sodium dodecylbenzenesulfonate;

[0024] The alcohol solvent is selected from one or more of ethanol, isopropanol, and ethylene glycol.

[0025] In an embodiment of the present invention, in S2, the process parameters of the spraying are as follows: the air pressure is 0.3 MPa - 0.5 MPa, the flow rate is 20 mL / min - 30 mL / min, the spraying distance is 200 mm - 400 mm, and the time is 40 s - 80 s.

[0026] In an embodiment of the present invention, in S3, the self - adsorption type plate freezer includes:

[0027] A first cavity with a microporous array on its surface; and the first cavity is connected with an air extraction pipe; the air extraction pipe is connected to a vacuum pump;

[0028] A second cavity located below the first cavity; the second cavity is provided with a perfusion port and an exhaust port; the perfusion port is used for perfusion of liquid nitrogen; the exhaust port is used for discharging the air in the second cavity.

[0029] In an embodiment of the present invention, in S3, the temperature of the liquid nitrogen freezing is - 150 °C to - 100 °C, and the time is 1 min - 2 min;

[0030] The vacuum degree of the freeze - drying is 2 Pa - 10 Pa, the temperature is - 20 °C to - 40 °C, and the time is 5 h - 10 h;

[0031] The vacuum degree of the plasma surface treatment is 20 Pa - 40 Pa, the power is 100 W - 150 W, and the time is 1 min - 5 min.

[0032] In an embodiment of the present invention, in S5, the measurement of the voltage distribution of the super - black composite film specifically includes the following steps: Connect the electrodes on the super - black composite film to a voltage acquisition circuit, use two adjacent electrodes as the input point and the output point of the exciting current, and simultaneously measure the voltage value between each remaining electrode and the current output point. Conduct current excitation between each pair of remaining adjacent electrodes in turn until all electrode pairs are tested, and obtain the voltage distribution at each electrode of the super - black composite film before damage.

[0033] In an embodiment of the present invention, in S6, the software used for image reconstruction is MATLAB software.

[0034] The technical solution of the present invention has the following advantages compared with the prior art:

[0035] (1) The ultra-black composite film described in the present invention has a multi-level and multi-stage composite light-trapping structure, including: a honeycomb hole array arranged vertically and orderly at the micron scale, and an uneven carbon nanotube continuous network that constitutes the honeycomb wall. This micro-nano honeycomb structure can generate multiple reflections and absorptions of incident light, and the uneven carbon nanotube honeycomb wall can perform multiple scattering on the incident light, so that the reflected light is greatly reduced, thereby obtaining ultra-absorbing ability.

[0036] (2) The ultra-black composite film described in the present invention has good electrical conductivity, making the ultra-black composite film a sensitive medium. When it is damaged, the change amplitude of its conductivity is large, and the local damage intelligent self-monitoring and positioning of the ultra-black composite film can be realized through the conductivity image reconstruction technology. Online monitoring can be realized without introducing external sensors, without affecting the optical performance of the ultra-black composite film itself.

[0037] (3) The method described in the present invention uses the two-step spraying-drying technology. After spraying the composite ink on the substrate for the first time and then performing heat drying treatment, a dense carbon nanotube film is formed on the film surface, which makes the ultra-black composite film have good electrical conductivity. For the second time, the composite ink is sprayed and then subjected to liquid nitrogen freezing and freeze-drying to form a layer with a honeycomb-like micro-nano light-trapping structure on the original dense carbon nanotube layer. On the one hand, it improves the optical performance of the film, making it an ultra-black composite film; on the other hand, although it reduces the overall electrical conductivity, due to the formation of a dense carbon nanotube film by the first spraying, the overall conductivity of the ultra-black composite film still has a good level. When collecting the voltage value after applying current excitation to the ultra-black composite film, the ultra-black composite film with better electrical conductivity has a greater change amplitude of conductivity after being damaged, and the position shown by the reconstruction of the conductivity image is also clearer and more accurate, thereby realizing the function that the ultra-black composite film can perform structural health self-sensing monitoring.

[0038] (4) The method described in the present invention combines the spraying technology, the freezing technology and the conductivity image reconstruction technology, and has the advantages of simple process flow, suitable for large-area preparation, accurate positioning, etc. Compared with the traditional offline detection, it is also faster and more convenient, and can significantly improve the early warning ability of the ultra-black composite film when it serves under complex conditions such as the space environment. Description of the Drawings

[0039] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention and in combination with the drawings, where:

[0040] Figure 1 It is a schematic diagram of the self-adsorbing plate freezer of the present invention;

[0041] Figure 2Schematic diagram of the intelligent detection device and imaging results of the super-black composite film in Embodiment 1 of the present invention; among them, (a) is the intelligent detection device diagram, (b) is the schematic diagram of the super-black composite film with through-hole damage, and (c) is the positioning imaging of the super-black composite film with through-hole damage;

[0042] Figure 3 Imaging results of the film in Comparative Example 1 of the present invention; among them, (a) is the schematic diagram of the super-black composite film with through-hole damage, and (b) is the positioning imaging of the super-black composite film with through-hole damage;

[0043] Figure 4 Macrophotographs of the super-black composite film of the present invention; among them, (a) is the macrophotograph of the super-black composite film before fixing the electrode, and (b) is the macrophotograph of the super-black composite film after connecting to the circuit;

[0044] Figure 5 SEM images of the microscopic morphology of the super-black composite film of the present invention; among them, (a) is the micron scale; (b) is the nanometer scale;

[0045] Figure 6 Integrating sphere diffuse reflectance of the super-black composite film of the present invention. Detailed implementation manners

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited are not intended to limit the present invention.

[0047] In the present invention, unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods without special instructions, and the materials, reagents, etc. used can be obtained from commercial channels without special instructions.

[0048] In the present invention, unless otherwise specified, the multi-walled carbon nanotubes used in the embodiments of the present invention are purchased from Qihang Technology, with a length of about 10 μm - 100 μm and a diameter of about 10 nm - 20 nm; the binder acrylic resin is purchased from Shanghai Tuyu New Materials Technology Co., Ltd., with the model number PQ673; the associative polyurethane thickener is purchased from Guangzhou Huitu New Materials Co., Ltd., with the model number HT-105; the polysiloxane defoamer is purchased from Guangzhou Tuosheng New Materials Co., Ltd., with the model number BYK-025; the electrode is an iron-plated copper electrode clip.

[0049] In the present invention, unless otherwise specified, the self-adsorbing plate freezer used in the embodiments of the present invention ( Figure 1)It includes: a first cavity 1 with a microporous array 1.1 opened on its surface; and an air extraction pipe 2 connected to the side wall of the first cavity 1. The air extraction pipe 2 can be connected to a vacuum pump; a second cavity 3 located below the first cavity 1 for charging and discharging cryogenic liquid nitrogen, so that the self-adsorption type freezing processor obtains a low temperature, and uses the low temperature created by liquid nitrogen to quickly freeze the wet composite film; a perfusion port 4 (funnel-shaped) is provided on the front side wall of the second cavity 3 for perfusion of liquid nitrogen; an exhaust port 5 is provided on the front side wall of the second cavity 3 for discharging the air in the second cavity 3.

[0050] Example 1

[0051] Refer to Figure 2 As shown, the intelligent detection method of the super-black composite film of the present invention specifically includes the following steps:

[0052] S1: Preparation of composite ink

[0053] S11. Preparation of multi-walled carbon nanotube color paste: Weigh 6 parts of multi-walled carbon nanotubes, 4 parts of surface modifier sodium dodecylbenzenesulfonate, 80 parts of water, and 10 parts of alcohol solvent isopropanol, add them to a dispersion tank, first use a mechanical shear disperser to stir and disperse at a stirring speed of 1000 rpm for 30 min, then use ultrasonic dispersion at a power of 500 W for 30 min, and then use a high-pressure homogenizer to disperse 5 times at a pressure of 800 bar to obtain multi-walled carbon nanotube color paste.

[0054] S12. Preparation of composite ink: Take 85 parts of multi-walled carbon nanotube color paste and add it to a dispersion tank containing 12 parts of deionized water, and use a mechanical shear disperser to stir and mix at a stirring speed of 2000 rpm for 60 min; continue to slowly add 5 parts of binder acrylic resin emulsion with a solid content of 40%, 1 part of metal oxide filler nano-titanium dioxide, 0.5 part of associative polyurethane thickener, 0.5 part of polysiloxane defoamer, and 1 part of auxiliary agent isopropanol under stirring conditions, and continue to stir and mix for 60 min to obtain composite ink.

[0055] S2: Preparation of composite film

[0056] S21. Use a low-temperature surface plasma with a power of 1 kW to treat for 20 s, and then pickle with 10% sulfuric acid by volume for 10 min to complete the hydrophilic treatment of the surface of the flexible polyimide film substrate to obtain a pretreated substrate;

[0057] S22. Through the spraying technique, set the air pressure to 0.3 MPa, the flow rate to 30 mL / min, the spraying distance to 250 mm, and the time to 10 s, spray the multi-walled carbon nanotube color paste on the surface of the pretreated substrate, and place it in an oven for drying treatment at 80°C for 30 min to obtain a dense film;

[0058] S23. By means of spraying technology, set the air pressure to 0.3 MPa, the flow rate to 30 mL / min, the spraying distance to 250 mm, and the time to 80 s, and spray the composite ink on the surface of the dense film to make a composite film;

[0059] S3: Preparation of super-black composite film

[0060] S31. Spread the composite film on the surface of a self-adsorbing plate freezer filled with liquid nitrogen and freeze it at -120 °C for 1 min;

[0061] S32. Then freeze-dry it in a freeze dryer at a vacuum degree of 5 Pa and a temperature of -40 °C for 8 h to form a vertically arranged micro-nano honeycomb structure through liquid nitrogen freezing and freeze drying;

[0062] S33. Finally, carry out oxygen plasma surface treatment for 5 min at a cabin vacuum degree of 40 Pa and a power of 120 W to etch the honeycomb walls at the top of the vertically and orderly arranged micro-nano honeycomb structure to obtain a super-black composite film;

[0063] S4. Cut the super-black composite film into a 10 cm × 10 cm square, and evenly clamp the electrode clips connected with wires around the film (4 electrodes on each side);

[0064] S5. Connect the electrodes on the super-black composite film to a voltage acquisition circuit, use two adjacent electrodes as the input point and output point of the excitation current (DC current is 100 mA), and at the same time measure the voltage value between each remaining electrode and the current output point. Conduct current excitation between each remaining adjacent electrode pair in turn until all electrode pairs are tested to obtain the voltage distribution at each electrode of the super-black composite film before damage;

[0065] Refer to respectively Figure 2 Damage the super-black composite film, and repeat this step for the damaged super-black composite film to obtain the voltage distribution of the damaged super-black composite film;

[0066] S6. Use the open-source EIDORS program in MATLAB software. According to parameters such as the size of the ultra-black composite film, the distribution position of electrodes, and the number of electrodes in the experiment, establish a calculation model identical to the experimental ultra-black composite film. Import the voltage distributions before and after the damage of the ultra-black composite film, perform image reconstruction, and obtain the conductivity distribution imaging map of the ultra-black composite film. According to the conductivity distribution, the structural state of the ultra-black composite film can be reflected, thereby realizing the intelligent self-monitoring and positioning of the damage of the ultra-black composite film. By measuring the voltage distributions before and after the damage and importing them into the model, the conductivity distribution maps of the film surface before and after the damage are obtained. In the damaged area, due to the destruction of the structure and the interruption of the conductive path, the conductivity decreases. The changing area on the conductivity distribution map corresponds to the area where the conductivity decreases. By observing the changes in the conductivity distribution map, the damage position on the film surface can be quickly detected.

[0067] Figure 2 It is a schematic diagram of the intelligent self-detection and positioning device for local damage of the ultra-black composite film and the imaging results. Among them, Figure 2 (a) is a schematic diagram of the damage detection and positioning device and the circuit connection (taking the 16-electrode conductivity image reconstruction device as an example). There are 4 electrodes evenly distributed on each side of the ultra-black composite film. The electrodes are connected to the device for providing excitation current and voltage detection through wires. The voltage measurement device can transmit the measured voltage value to the computer terminal. When the ultra-black composite film has holes due to being impacted by an external object, its surface structure is damaged. Under the same current excitation, the voltage values measured at each electrode change. Transmit the voltage values before and after the damage to the computer terminal. According to the open-source EIDORS program in MATLAB, establish a model identical to the test sample and the connected electrodes, and input the voltage distributions before and after the damage to obtain the change map of the overall conductivity of the ultra-black composite film. Figure 2 (b) is a schematic diagram of the ultra-black composite film after being connected to the test device, with a through-hole damage made on the film. Figure 2 (c) is the conductivity change image of the ultra-black composite film obtained by collecting voltage values and reconstructing the conductivity image. The conductivity change area basically coincides with the actual damaged position, indicating that this method can well monitor and locate the damage on the ultra-black film.

[0068] Comparative Example 1

[0069] It is basically the same as Example 1, except that: a dense film is not prepared.

[0070] The imaging results of the composite film are as Figure 3 shown. From Figure 3It can be seen that for the film obtained by directly spraying the composite ink without spraying the carbon nanotube paste and then freeze-drying, due to the lack of a dense carbon nanotube layer, the overall conductivity is poor. Under the same current excitation, the measured voltage signal is weak and the error is large. When reconstructing the image by importing it into the MATLAB model, due to the large error, there is a large error in the positioning and detection ability of the damaged position on the film.

[0071] Test Example 1

[0072] Figure 4 (a) is the macroscopic optical photograph of the super-black composite film before fixing the electrodes. The super-black composite film is overall dark black, with uniform color and no visible reflection to the naked eye. Figure 4 (b) is the macroscopic optical photograph of the super-black composite film after connecting to the circuit. Since the fixed electrodes only occupy a small area around the super-black composite film, the overall optical properties of the super-black composite film will not be affected.

[0073] Test Example 2

[0074] The SEM characterization of the microstructure of the super-black composite film was carried out, and the results are as Figure 5 shown. From Figure 5 (a), it can be seen that on the micron scale, the super-black composite film prepared by this method presents a biomimetic honeycomb porous structure. The diameter distribution of the honeycomb holes is about 10μm - 50μm. This vertical hole structure enables light to undergo multiple absorption-reflections inside it, and can effectively "capture" light. From Figure 5 (b), it can be seen that on the nanoscale, the carbon nanotubes in the honeycomb skeleton are intertwined with each other, forming a continuous and loose carbon nanotube network. On the one hand, the nano-pores can further scatter light, and on the other hand, the carbon nanotubes are in contact with each other, forming a good electron transport channel and becoming a good conductive whole.

[0075] Test Example 3

[0076] Using a LAMBDA 1050+ ultraviolet-visible-near-infrared spectrophotometer with an integrating sphere attachment, the integrating sphere diffuse reflectance curve of the super-black composite film was measured, and the wavelength range was 400nm - 2000nm. The results are as Figure 6 shown. From Figure 6 it can be seen that the average reflectance of the super-black composite film in the visible and near-infrared (Vis / NIR) bands is ~0.4% (absorptance ~99.6%).

[0077] In summary, this vertically arranged bionic micro-nano honeycomb structure of the super-black composite film can perform multiple reflections-absorptions and multiple scatterings on incident light, obtaining super light absorption ability. In addition, multi-walled carbon nanotubes form a honeycomb structure under the extrusion of ice crystals. As the main body of the honeycomb skeleton, the multi-walled carbon nanotubes with a large aspect ratio are intertwined with each other, becoming good electron transport channels and forming an overall and continuous conductive network. When damage occurs on the super-black composite film, the structure of the damaged area is destroyed, resulting in the interruption of the conductive network in this area and a change in conductivity. By measuring the voltage values at each electrode position and using the conductivity image reconstruction method, the conductivity distribution image of the entire super-black composite film can be visualized, and the structural changes can be reflected by the change in conductivity before and after damage. Thus, the in-situ and online self-sensing structural health monitoring of the super-black composite film can be realized without affecting its normal use, achieving real-time structural sensing, damage monitoring, and positioning of the super-black composite film.

[0078] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. An intelligent detection method for ultra-black composite film, characterized in that: The following steps are involved: S1, spraying a multi-walled carbon nanotube color paste on the surface of a substrate, and obtaining a dense film after drying; S2. Spraying the composite ink on the surface of the dense film to form a composite film; the mass parts of the components in the composite ink are: 70-90 parts of multi-walled carbon nanotube color paste, 5-15 parts of water, 1-5 parts of binder, 1-5 parts of metal oxide filler, 0.5-1 parts of thickener, 0.5-1 parts of defoamer, and 1-5 parts of additive; the mass ratio of multi-walled carbon nanotubes, surface modifier, water and alcohol solvent in the multi-walled carbon nanotube color paste is (5-10):(4-10):(70-90):(5-12); S3, freezing the composite film with liquid nitrogen by a self-adsorption flat plate freezer, and then freeze-drying the composite film by a freeze dryer, and obtaining an ultra-black composite film by plasma surface treatment; S4, electrodes are drawn out around the ultra-black composite film, and the number of electrodes on each side is 4 or 6; S5, connecting the electrodes on the ultra-black composite film to a voltage acquisition circuit, using two adjacent electrodes as input points and output points of the excitation current, measuring the voltage values ​​at the remaining electrodes, and obtaining the voltage distribution at each electrode of the ultra-black composite film before damage; Repeating the steps for the damaged ultra-black composite film to obtain the voltage distribution of the damaged ultra-black composite film; S6. Reconstruct an image based on the voltage distribution before and after the ultra-black composite film is damaged to obtain a distribution imaging diagram of the conductivity of the ultra-black composite film; and realize intelligent self-monitoring and positioning of local damage of the ultra-black composite film based on the distribution imaging diagram.

2. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S1, the process parameters of the spraying are: air pressure of 0.3MPa-0.5MPa, flow rate of 20mL / min-30mL / min, spraying distance of 200mm-400mm, and time of 10s-20s; The drying temperature is 80°C-100°C, and the drying time is 20min-30min.

3. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S2, the preparation of the composite ink includes the following steps: dissolving the multi-walled carbon nanotube color paste described in S1 in water and stirring evenly, and continuing to add a binder, a metal oxide filler, a thickener, a defoaming agent and an auxiliary agent and stirring evenly to obtain a composite ink; the multi-walled carbon nanotube color paste is obtained by mixing multi-walled carbon nanotubes, a surface modifier, water and an alcohol solvent.

4. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S2, the binder is selected from one or more of acrylic resin, silicone-modified acrylic resin and epoxy resin; The metal oxide filler is selected from nano zinc oxide and / or nano titanium dioxide; The thickener is selected from hydroxyethyl cellulose and / or associative polyurethane thickener; The defoamer is selected from polysiloxane defoamer and / or BASF Formato defoamer; The auxiliary agent is selected from isopropanol and / or ethylene glycol; The surface modifier is selected from one or more of disodium distyryl diphenyl disulfonate, polyvinyl pyrrolidone and sodium dodecylbenzene sulfonate; The alcohol solvent is selected from one or more of ethanol, isopropanol and ethylene glycol.

5. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S2, the process parameters of the spraying are: air pressure of 0.3MPa-0.5MPa, flow rate of 20mL / min-30mL / min, spraying distance of 200mm-400mm, and time of 40s-80s.

6. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S3, the self-adsorption plate freezer comprises: The first cavity has a micropore array on its surface; the first cavity is connected to an exhaust pipe; the exhaust pipe is connected to a vacuum pump; The second cavity is located below the first cavity; the second cavity is provided with an infusion port and an exhaust port; the infusion port is used for infusing liquid nitrogen; the exhaust port is used for exhausting the air in the second cavity.

7. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S3, the temperature of the liquid nitrogen freezing is -150°C to -100°C, and the time is 1 min to 2 min; The freeze drying process has a vacuum degree of 2Pa-10Pa, a temperature of -20°C to -40°C, and a time of 5h-10h; The plasma surface treatment has a vacuum degree of 20Pa-40Pa, a power of 100W-150W, and a time of 1min-5min.

8. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S5, the measurement of the voltage distribution of the ultra-black composite film specifically includes the following steps: connecting the electrodes on the ultra-black composite film to the voltage acquisition circuit, using two adjacent electrodes as the input point and output point of the excitation current, and measuring the voltage value between each remaining electrode and the current output point at the same time, and performing current excitation between each remaining adjacent electrode pair in turn until all electrode pairs are tested, thereby obtaining the voltage distribution at each electrode of the ultra-black composite film before damage.

9. The intelligent detection method of ultra-black composite film according to claim 1, characterized in that: In S6, the software used for image reconstruction is MATLAB software.

Images