Broadband wave-absorbing OSR secondary surface mirror and preparation method thereof

Abstract

The invention provides a broadband wave-absorbing OSR secondary surface mirror and a preparation method thereof. The broadband wave-absorbing OSR secondary surface mirror comprises a protective layer, a reflecting layer, a base material and a resonance unit layer which are stacked, the reflection layer is a metal silver plating layer with reflection capability in visible light and near-infrared bands, the protection layer is a chromium-plated alloy plating layer, the resonance unit layer is an ITO hollow pattern, broadband wave absorption is realized through impedance matching and multimode resonance, and the resonance unit layer has light transmission capability in the visible light band. The wave-absorbing material is simple and reasonable in structure, light in additional weight and high in implementability, can be flexibly applied to the surface of a satellite structure, has a wide-frequency-band wave-absorbing function on the basis of not influencing the thermal control performance, and can effectively reduce the radar cross section of the satellite surface.

Description

Technical Field

[0001] The present invention relates to the field of spacecraft materials, and in particular to an OSR secondary surface mirror with wide-band wave absorption and a preparation method thereof. Background Art

[0002] The OSR (optical solar reflecor) secondary surface mirror is a composite surface, usually composed of a surface layer that is transparent to visible light and a vacuum-coated metal bottom layer that reflects visible light. It has a very low solar absorption ratio and a very low absorption-emission ratio. It is installed on the surface of a satellite and has a high reflectivity to the solar spectrum. It can reflect most of the solar radiation energy, thereby reducing the temperature rise caused by strong sunlight on satellites and other spacecraft. At the same time, it has a very high emissivity and can emit the waste heat inside the satellite, which can reduce the ambient temperature of the onboard instruments and keep them in the normal working temperature range.

[0003] With the development of space target detection systems, the demand for satellite stealth is becoming increasingly stronger. The secondary surface mirror on the satellite surface usually has a high radar cross section and is easily captured by space-based or ground-based detection radars. It is necessary to develop a satellite secondary surface mirror with a low RCS (Radar Cross section) surface.

[0004] In the Chinese patent document with publication number CN117406322A, a UV-reflective glass type secondary surface mirror and a preparation method thereof are disclosed. However, the secondary surface mirror does not have a wave absorbing function.

[0005] In the Chinese patent document with the announcement number CN114465016B, an ultra-thin light-transmitting metamaterial absorber for X-band stealth is disclosed, but its stealth band is relatively single and cannot have thermal control function. There is no report on a secondary surface mirror that has both satellite thermal control and microwave absorption functions.

[0006] Therefore, a secondary surface mirror that combines satellite thermal control and microwave absorption functions is needed to solve the above problems. Summary of the invention

[0007] In view of the defects in the prior art, an object of the present invention is to provide an OSR secondary surface mirror with wide-band absorbing properties and a method for preparing the same.

[0008] According to the present invention, a wide-band absorbing OSR secondary surface mirror comprises: a stacked protective layer, a reflective layer, a substrate and a resonant unit layer;

[0009] The substrate is made of transparent glass, the reflective layer is arranged on the upper surface of the substrate, the resonance unit is arranged on the lower surface of the substrate, and the protective layer is arranged on the upper surface of the reflective layer;

[0010] The reflective layer is a metal silver coating with reflective capabilities in the visible light and near-infrared bands, the protective layer is a chrome alloy coating, and the resonant unit layer is an ITO hollow pattern. Wide-band wave absorption is achieved through impedance matching and multi-mode resonance, and the resonant unit layer has light transmittance in the visible light band.

[0011] Preferably, the substrate thickness is 2 mm, and the substrate size is 40 mm×40 mm; the reflective layer thickness is 150-400 nm, and the protective layer thickness is 200-500 nm; the resonance unit layer thickness is 40-50 nm, and the square resistance of the resonance unit layer is 1-1.8 kΩ / □.

[0012] Preferably, the resonant unit layer is formed by placing a mask on a substrate to construct a hollow structure, the mask is a connected structure, the size of the mask is 15 mm×15 mm, and it is symmetrically arranged.

[0013] Preferably, the secondary surface mirror is pasted on the surface of the satellite structure, the gap between the secondary surface mirrors is less than 0.2 mm, and the ITO pattern of the secondary surface mirror maintains the same direction.

[0014] A method for preparing a broadband absorbing OSR secondary surface mirror according to the present invention comprises:

[0015] Step S1: selecting a substrate for manufacturing a secondary surface mirror, and inspecting, cleaning and drying it;

[0016] Step S2: coating one surface of the substrate with a silver reflective layer;

[0017] Step S3: replacing the target material and plating a nickel-chromium alloy protective layer on the surface of the reflective layer;

[0018] Step S4: processing a mask for manufacturing a resonance unit layer;

[0019] Step S5: placing a stainless steel mask on the uncoated surface of the substrate, and using a positioning tool to make the mask coincide with the center of the substrate;

[0020] Step S6: plating an ITO layer on the mask and plating a furnace sample at the same time; the furnace sample uses the same substrate;

[0021] Step S7: Use a four-probe resistance meter to test the surface sheet resistance of the furnace sample. If the sheet resistance meets the requirements, the preparation is completed. Otherwise, re-preparation is performed.

[0022] Preferably, in step S2, step S3, and step S6, a vacuum magnetron sputtering deposition system is used for film coating, and different film layers are deposited by replacing the target material and adjusting the parameters.

[0023] Preferably, the vacuum equipment is evacuated before coating to a vacuum degree of less than 10 -4 Pa level; when plating the silver layer, control the power to 0.6~1kW and the temperature to 20~100℃; when plating the ITO layer, control the oxygen content to 2%~5%, the power to 0.6~1kW and the temperature to 200~400℃.

[0024] Preferably, in step S4, the mask is processed by laser cutting of stainless steel, with a thickness of 1 mm and a dimensional tolerance of ±0.1 mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention has a simple and reasonable structure, small additional weight, strong feasibility, and can be flexibly applied to the surface of satellite structures. On the basis of not affecting the thermal control performance, it has a wide-band wave absorbing function and can effectively reduce the radar scattering cross section of the satellite surface.

[0027] 2. The present invention has a thin thickness, a wide absorption bandwidth, is insensitive to the polarization direction of the incident electromagnetic wave, and can design different resonant unit structures according to the radar detection band, and achieve efficient absorption in different scenarios through parameter control.

[0028] 3. The present invention can be widely used in the fields of spacecraft radar stealth, electromagnetic shielding, electromagnetic protection, etc., and has strong compatibility with existing thermal control systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0030] Figure 1 It is a schematic diagram of the structure of the wide-band absorbing OSR secondary surface mirror in the present invention;

[0031] Figure 2 It is a schematic diagram of the OSR secondary surface mirror resonance unit layer for wide-band wave absorption in the present invention;

[0032] Figure 3 The figure is a schematic diagram of the preparation process of the wide-band absorbing OSR secondary surface mirror in the present invention.

[0033] Description of reference numerals:

[0034] DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0036] The present invention provides an OSR secondary surface mirror with wide-band wave absorption, which consists of four layers: a substrate 1, a reflection layer 2, a protective layer 3, and a resonance unit layer 4. The substrate 1 is made of quartz glass or cerium glass and has extremely high visible light transmittance; the reflection layer 2 is a metal silver plating layer with high reflectivity in the visible light and near-infrared bands, the protective layer 3 is a nickel-chromium alloy plating layer that protects the reflection layer 2 and the substrate 1, and the resonance unit layer 4 is an ITO hollow pattern. Through impedance matching and multi-mode resonance, wide-band wave absorption is achieved. At the same time, ITO has high transmittance in the visible light band and does not affect the overall thermal control performance.

[0037] In a specific embodiment, the cerium glass is 2 mm thick and has a size of 40 mm×40 mm; the silver reflective layer 2 is about 150 nm thick and opaque; the nickel-chromium alloy plating layer is about 200 nm thick; the ITO film is about 50 nm thick and has a sheet resistance of 1 kΩ / □. The resonant unit layer 4 is plated with a hollow pattern by placing a stainless steel mask on the substrate 1. The mask is a connected structure, which is easy to process and position. The overall size of the mask is 15 mm×15 mm and is symmetrical. The wide-band absorbing OSR secondary surface mirror is pasted on the surface of the satellite structure. The gap between the secondary surface lenses is less than 0.2 mm, and the ITO pattern of the secondary surface mirror maintains the same direction.

[0038] The working principle of the broadband absorbing OSR secondary surface mirror provided by the present invention is:

[0039] The wide-band absorbing OSR secondary surface mirror is an electromagnetic metamaterial absorber that can absorb incident electromagnetic waves at the working wavelength and convert them into ohmic heat or other forms of energy. It is a three-layer structure, with a surface structure composed of periodically arranged ITO resistor film units, a dielectric substrate in the middle, and a complete metal coating as a reflective layer 2. When the input impedance of the OSR overall unit structure matches that of the air, all electromagnetic waves are incident on the OSR body without reflection. The electromagnetic waves cannot pass through the reflective layer 2 and are reflected back by the reflective layer 2, interfering with the subsequent incident waves.

[0040] By adjusting the structural parameters and material properties of OSR, the equivalent magnetic permeability and equivalent dielectric constant can be adjusted to achieve maximum absorption of electromagnetic waves. The overall energy loss of OSR is mainly concentrated in the ITO film, which relies on ohmic loss to convert electromagnetic waves into other forms of energy to increase the absorption rate of electromagnetic waves. The ITO block resistance reflects the conductive properties and is a key factor affecting the equivalent input impedance and ohmic loss. The OSR secondary surface mirror with wide-band absorption is thin, has a wide absorption bandwidth, and is insensitive to the polarization direction of the incident electromagnetic wave.

[0041] The present invention provides a method for preparing a wide-band absorbing OSR secondary surface mirror, which specifically comprises the following steps:

[0042] Step S1: inspecting, cleaning, and drying the glass substrate 1;

[0043] Step S2: Place the substrate 1 into the coating tooling and evacuate the substrate to a vacuum level of less than 10 -4 Pa, silver-plated reflective layer 2, power set to 0.6 kW, temperature set to 40 °C;

[0044] Step S3: Replace the target material, plate the nickel-chromium alloy protective layer 3, set the power to 0.6 kW, and set the temperature to 40° C. After the coating is completed, take out the substrate 1 and turn it over;

[0045] Step S4: Laser cutting of stainless steel processing mask with a thickness of 1 mm and a dimensional tolerance of ±0.1 mm;

[0046] Step S5: placing a stainless steel mask on the uncoated surface of the glass substrate 1, and aligning the mask with the center of the glass substrate 1 by using a suitable positioning tool;

[0047] Step S6: Put the substrate back into the coating equipment, and place the furnace sample of the same substrate 1 at the same time, and evacuate the vacuum to less than 10 -4 Pa, ITO layer is plated, and the furnace sample is plated at the same time. The oxygen content is set to 3%, the power is 1kW, and the temperature is 200℃. After the coating is completed, the secondary surface mirror is taken out;

[0048] Step S7: Use a four-probe resistance meter to test the sheet resistance of the furnace sample surface. If the sheet resistance meets the requirement, the prepared OSR secondary surface mirror can be saved. Otherwise, it needs to be re-prepared.

[0049] The prepared OSR secondary surface mirror was tested for wave absorption and thermal control performance. In a microwave darkroom, the S parameters of the OSR were tested using a vector network analyzer and noise was removed. The measured wave absorption rate in the 18.6GHz to 29.1GHz frequency band was better than 90%. The tested OSR solar absorption ratio was 0.18 and the hemispherical emissivity was 0.79, which met the satellite thermal control requirements.

[0050] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0051] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A broadband absorbing OSR secondary surface mirror, characterized in that: include: A protective layer (3), a reflective layer (2), a substrate (1), and a resonant unit layer (4) arranged in a stacked manner; The substrate (1) is made of transparent glass, the reflective layer (2) is arranged on the upper surface of the substrate (1), the resonant unit is arranged on the lower surface of the substrate (1), and the protective layer (3) is arranged on the upper surface of the reflective layer (2); The reflective layer (2) is a metallic silver coating having reflective capabilities in the visible light and near-infrared bands, the protective layer (3) is a chrome alloy coating, and the resonant unit layer (4) is an ITO hollow pattern, which realizes wide-band wave absorption through impedance matching and multi-mode resonance, and the resonant unit layer (4) has light transmission capabilities in the visible light band.

2. The broadband absorbing OSR secondary surface mirror according to claim 1, characterized in that: The thickness of the substrate (1) is 2 mm, and the size of the substrate (1) is 40 mm×40 mm; the thickness of the reflective layer (2) is 150 to 400 nm, and the thickness of the protective layer (3) is 200 to 500 nm; the thickness of the resonant unit layer (4) is 40 to 50 nm, and the square resistance of the resonant unit layer (4) is 1 to 1.8 kΩ / □.

3. The broadband absorbing OSR secondary surface mirror according to claim 1, characterized in that: The resonant unit layer (4) is formed by placing a mask on the substrate (1) to construct a hollow structure, the mask is a connected structure, the size of the mask is 15 mm×15 mm, and it is symmetrically arranged.

4. The broadband absorbing OSR secondary surface mirror according to claim 1, characterized in that: The secondary surface mirror is pasted on the surface of the satellite structure, the gap between the secondary surface lenses is less than 0.2 mm, and the ITO pattern of the secondary surface mirror keeps the same direction.

5. A method for preparing a broadband absorbing OSR secondary surface mirror, characterized in that: include: Step S1: selecting a substrate (1) for manufacturing a secondary surface mirror, and inspecting, cleaning and drying it; Step S2: plating a silver reflective layer (2) on one surface of the substrate (1); Step S3: replacing the target material and plating a nickel-chromium alloy protective layer (3) on the surface of the reflective layer (2); Step S4: processing a mask for manufacturing the resonance unit layer (4); Step S5: placing a stainless steel mask on the uncoated surface of the substrate (1), and using a positioning tool to make the mask coincide with the center of the substrate (1); Step S6: coating the mask with an ITO layer and simultaneously coating a furnace sample; the furnace sample uses the same substrate (1); Step S7: Use a four-probe resistance meter to test the surface sheet resistance of the furnace sample. If the sheet resistance meets the requirements, the preparation is completed. Otherwise, re-preparation is performed.

6. The method for preparing a broadband absorbing OSR secondary surface mirror according to claim 5, characterized in that: In step S2, step S3, and step S6, a vacuum magnetron sputtering deposition system is used for film coating, and different film layers are deposited by replacing the target material and adjusting the parameters.

7. The method for preparing a broadband absorbing OSR secondary surface mirror according to claim 6, characterized in that: Before coating, evacuate the vacuum equipment to make the vacuum degree less than 10 -4 Pa level; when plating the silver layer, control the power to 0.6~1kW and the temperature to 20~100℃; when plating the ITO layer, control the oxygen content to 2%~5%, the power to 0.6~1kW and the temperature to 200~400℃.

8. The method for preparing a broadband absorbing OSR secondary surface mirror according to claim 6, characterized in that: In step S4, a stainless steel processing mask is cut by laser, with a thickness of 1 mm and a dimensional tolerance of ±0.1 mm.

Images