Double-layer structure infrared stealth material based on high-temperature resistant metal and preparation method thereof

Abstract

A double-layer infrared stealth material based on high-temperature resistant metal and its preparation method are designed by using Mo, a metal with excellent infrared properties, high temperature resistance, and good thermal stability. The absorptivity of the two-layer membrane structure is calculated using a transmission matrix to obtain the absorption spectrum under normal incidence. The present invention can well match the atmospheric infrared window, with a high absorptivity in the atmospheric window band and a relatively low absorptivity in the infrared window band with high atmospheric transmittance. It well meets the actual needs of the target for selective infrared radiation stealth. The optimized structure is prepared by magnetron sputtering and other methods, and the infrared absorption spectrum of the obtained sample is measured. The measurement results are consistent with the results obtained by theoretical calculation, proving the feasibility of the present invention in practical use, especially the practical significance of achieving stealth function in high-temperature environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of infrared stealth materials, and in particular relates to a double-layer infrared stealth material based on high-temperature resistant metal and a preparation method thereof. Background Art

[0002] With the rapid development of science and technology, infrared detection technologies and means have gradually become more abundant. At the same time, the precision and accuracy of infrared detection equipment have been continuously improved. How to make the target invisible or "invisible" under the increasingly mature infrared detection system has gradually aroused widespread attention.

[0003] As we all know, all objects with a temperature above absolute zero emit infrared radiation. According to Stefan-Boltzmann's law, the infrared radiation emitted by an object is proportional to the fourth power of its surface absolute temperature. Therefore, when an object's temperature is higher than its surroundings, its infrared radiation will be significantly enhanced, making it a very conspicuous target for infrared detection and imaging systems. Infrared stealth technology, on the other hand, can modify the infrared radiation signature of a target through certain technical means, making the target's infrared radiation identical or similar to that of the background environment within the detection range of the infrared detection system, thereby rendering the target invisible or "invisible" within the detection range. Therefore, infrared stealth technology can regulate the target's infrared radiation, thereby reducing the probability of the target being detected by the infrared detection system, thereby achieving the target's stealth function within the infrared detection system.

[0004] According to Kirchhoff's law, for an object in thermal equilibrium, its emissivity and absorptivity are equal. Therefore, regulating the emissivity of the target surface is equivalent to regulating the absorptivity. By regulating the infrared stealth performance of a target through various infrared stealth technologies, the target can be made invisible under infrared detection. Therefore, people are vigorously researching and developing various infrared stealth technologies, and infrared stealth technology has gradually become a hot topic among scientists. In general, the target achieves infrared stealth mainly by using infrared stealth materials to control its own infrared radiation characteristics. In particular, for the atmospheric window band where current infrared detection systems operate, certain technical means are used to reduce the target's infrared emissivity in the atmospheric window, thereby reducing the probability of detection by the detection system, making the target invisible or "stealth."

[0005] Currently, traditional infrared stealth materials achieve stealth and camouflage by reducing the target's emissivity within the infrared band. While this approach can reduce an object's infrared radiation and the likelihood of detection to a certain extent, the reduced emissivity causes the object's heat to accumulate, causing its temperature to rise, which in turn increases its infrared radiation. Therefore, simply changing the object's emissivity in the infrared window to achieve infrared stealth is significantly insufficient and cannot meet practical needs.

[0006] The recent rise of metamaterials has paved the way for addressing this problem. Electromagnetic metamaterials (abbreviated as metamaterials) are artificial micro-nanostructures with artificially designed structures at the subwavelength scale, exhibiting extraordinary physical properties not found in natural materials. One typical application of metamaterials is the design of wavelength-selective absorbers. By adjusting the size and geometry of the metamaterial structure, the desired dielectric constant or magnetic permeability can be achieved, thereby controlling the location of the structure's resonant absorption peak in the infrared, microwave, and other wavelength bands, ultimately achieving wavelength-selective absorption. Through metamaterial structural design, the absorption and emission characteristics of a target can be controlled, thereby reducing the target's infrared stealth emissivity in the atmospheric window and increasing its radiative dissipation emissivity in the non-atmospheric window, thereby enabling the design of new infrared stealth materials. Metamaterial stealth has become a research hotspot in the field of stealth technology. However, with the continuous advancement of science and technology, the requirements for achieving infrared stealth are increasing. Due to the needs of practical applications, targets often need to operate in higher temperature environments, placing higher demands on the thermal stability of the structures that achieve infrared stealth. Furthermore, the preparation of simple and large-scale integrated infrared stealth materials has become a vexing problem. Summary of the Invention

[0007] To this end, the present invention provides a double-layer structure infrared stealth material based on high-temperature resistant metal and a preparation method thereof, which solves the problem in the prior art that due to the reduction of emissivity, the heat of the object continues to accumulate, causing the temperature of the object to continue to rise, which in turn causes the infrared radiation of the object to continue to increase; and the problem that the stealth material has low thermal stability and cannot maintain stable operation in a higher temperature environment to achieve the stealth function.

[0008] In order to achieve the above-mentioned object, the present invention provides the following technical solution: a double-layer structure infrared stealth material based on high-temperature resistant metal, comprising a high-temperature resistant lower layer and an anti-reflection upper layer; the high-temperature resistant lower layer is made of metal Mo; the anti-reflection upper layer is made of metal Ge;

[0009] The thickness of the high temperature resistant lower layer is greater than the skin depth of the incident light;

[0010] The thickness of the anti-reflection upper layer is adjusted according to the resonance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer.

[0011] As a preferred solution for a double-layer infrared stealth material based on high-temperature resistant metal, the thickness H1 of the high-temperature resistant lower layer is greater than the skin depth of the incident plane wave of the incident light, so that the transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer approaches zero.

[0012] As a preferred solution of a double-layer infrared stealth material based on high-temperature resistant metal, the absorptivity calculation formula of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer is:

[0013] A=1-TR

[0014] Where R, T and A are the reflectivity, transmittance and absorptivity of the structure, respectively.

[0015] The present invention also provides a method for preparing a double-layer structure infrared stealth material based on high-temperature resistant metal, comprising the following steps:

[0016] The absorptivity, refractive index, and transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer are calculated using a transmission matrix combined with simulation software to obtain an absorption spectrum of the structure under normal incidence. The absorption spectrum is used to characterize the relationship between the absorptivity of the structure and the wavelength of the incident light.

[0017] The thickness of the high-temperature resistant lower layer and the anti-reflection upper layer of the structure is adjusted, the absorption spectrum of the structure at the set thickness is calculated, and the optimized thickness of the structure is obtained. The optimized structure is prepared by magnetron sputtering and electron beam evaporation.

[0018] As a preferred solution for the preparation method of a double-layer infrared stealth material based on high-temperature resistant metal, the absorption rate, refractive index and transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer are calculated using the transmission matrix combined with simulation software. A plane wave with a wavelength range of 3 to 12 μm is defined to be vertically incident on the surface of the structure, and the left and right ends of the structure are set as periodic boundary conditions, and the upper and lower ends of the structure are set as port conditions.

[0019] As a preferred solution for the preparation method of a double-layer structure infrared stealth material based on high-temperature resistant metal, the thickness of the high-temperature resistant lower layer and the anti-reflection upper layer of the structure are adjusted so that the impedance of the structure matches the air impedance, so that the reflectivity of the structure is 0.

[0020] As a preferred solution for the preparation method of a double-layer structure infrared stealth material based on high-temperature resistant metal, the absorption rate of the structure in the atmospheric window is lower than the absorption rate of the structure in the non-atmospheric window.

[0021] As a preferred solution for the preparation method of a double-layer structure infrared stealth material based on high-temperature resistant metal, in the process of preparing the optimized structure by magnetron sputtering and electron beam evaporation, metal Mo and metal Ge are deposited in sequence on the silicon wafer;

[0022] The sputtering power of metal Mo is 100W, the working pressure is 0.5Pa, and the deposition rate is about 10nm / min;

[0023] The sputtering power of metal Ge is 150W, the working pressure is 0.5Pa, and the deposition rate is about 20.5nm / min.

[0024] The present invention has the following advantages: by adopting metal Mo with excellent infrared characteristics, high temperature resistance and good thermal stability, a new infrared stealth material based on high temperature resistant metal Mo is designed; the stealth material structure is composed of two layers of Mo / Ge film; and the absorptivity of the two-layer film structure is calculated through the transmission matrix to obtain the absorption spectrum under normal incidence. From the calculation results, the present invention can be well matched with the atmospheric infrared window, with a high absorptivity in the non-atmospheric window band and a relatively low absorptivity in the infrared window band with high atmospheric transmittance; it well meets the actual needs of the target for selective radiation infrared stealth; and the structure is simple and easy to prepare. The optimized structure is prepared by magnetron sputtering and other methods, and the infrared absorption spectrum of the obtained sample is measured. From the measurement results, it can be consistent with the results obtained by theoretical calculation, which proves the feasibility of the present invention in practical use, especially the practical significance of realizing the stealth function in a high temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0026] Figure 1 A schematic diagram of the structure of a double-layer infrared stealth material based on high-temperature resistant metal provided in an embodiment of the present invention and a cross-sectional view in the xz plane;

[0027] Figure 2 This is a graph showing the relationship between the absorptivity and wavelength of a double-layer infrared stealth material based on high-temperature resistant metal under normal incidence provided in an embodiment of the present invention;

[0028] Figure 3This is a field distribution diagram of the double-layer infrared stealth material based on high-temperature resistant metal provided in an embodiment of the present invention at the resonance absorption peak;

[0029] Figure 4 The following are photos of the experimental samples prepared in the examples of the present invention under a scanning electron microscope (SEM);

[0030] Figure 5 This is the absorption spectrum of the experimental sample prepared in the embodiment of the present invention measured by Fourier infrared spectrometer. DETAILED DESCRIPTION

[0031] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0032] See also Figure 1 An embodiment of the present invention provides a double-layer infrared stealth material based on a high-temperature-resistant metal structure, comprising a high-temperature-resistant lower layer and an anti-reflection upper layer. The high-temperature-resistant lower layer is made of metal Mo, and the anti-reflection upper layer is made of metal Ge. The thickness of the high-temperature-resistant lower layer is greater than the skin depth of incident light, and the thickness of the anti-reflection upper layer is adjusted based on the resonance of the structure formed by the high-temperature-resistant lower layer and the anti-reflection upper layer. According to impedance matching theory, adjusting the thickness of the structure can control the position of the structure's resonant absorption peak. Selecting an appropriate thickness can adjust the position of the structure's resonant absorption peak to the non-atmospheric window band, thereby achieving infrared stealth.

[0033] Specifically, the high-temperature metal-based double-layer infrared stealth material consists of two films: a simple high-temperature resistant lower layer and an anti-reflection upper layer. The structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer extends in the x and y directions. The bottom of the structure is a Mo substrate with a thickness greater than the skin depth of the incident plane wave, ensuring that the structure has almost zero transmittance for incident light. The upper layer of the structure is an anti-reflection layer composed of Ge, a high-refractive-index medium.

[0034] Here, H1 and H2 represent the thicknesses of the high-temperature-resistant lower layer formed by metal Mo and the anti-reflection upper layer formed by metal Ge, respectively. The thickness of H1 is greater than the skin depth of the incident light, ensuring that the structure's transmittance to incident light is almost zero. The thickness of H2 can be adjusted based on the structure's resonance requirements.

[0035] In this embodiment, a method for preparing a double-layer infrared stealth material based on high-temperature resistant metal is also provided, comprising the following steps:

[0036] S1. Calculate the absorptivity, refractive index, and transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer using a transmission matrix combined with simulation software to obtain an absorption spectrum of the structure under normal incidence, and characterize the relationship between the absorptivity of the structure and the wavelength of the incident light using the absorption spectrum.

[0037] S2. Adjust the thickness of the high-temperature resistant lower layer and the anti-reflection upper layer of the structure, calculate the absorption spectrum of the structure at the set thickness, obtain the optimized thickness of the structure, and prepare the optimized structure by magnetron sputtering and electron beam evaporation.

[0038] In this example, the absorption spectrum of the structure was numerically calculated using simulation software. Because the structure can extend in the x and y directions, the calculation was performed on a cross-section of the unit structure in the xz plane. During the simulation, a plane wave with a wavelength range of 3 to 12 μm was defined as perpendicularly incident on the surface of the structure. Periodic boundary conditions were set at the left and right ends of the structure, and port conditions were set at the top and bottom of the structure. The absorptivity of the structure can be calculated as A = 1 - TR, where R, T, and A are the reflectivity, transmittance, and absorptivity of the structure, respectively.

[0039] Since the thickness of the high temperature resistant lower layer is sufficient, the transmittance T can be considered to be almost 0. Therefore, by selecting the appropriate thickness of the high temperature resistant lower layer, the impedance of the structure is matched with that of the air, and the reflectivity of the structure can be made 0, thus achieving a perfect absorption close to 100%. Since the structure is highly symmetrical, it is polarization independent. For incident light of different polarization states under normal incidence, the absorption of the structure is the same. Figure 2 From the relationship diagram between the absorptivity of the structure and the wavelength of the incident light under normal incidence, it can be seen that the present invention can well match the atmospheric absorption spectrum, has a low absorptivity in the atmospheric window, can realize the infrared stealth function, and has a high absorptivity and a wide absorption bandwidth in the non-atmospheric window, which can better realize radiative heat dissipation in the non-atmospheric window.

[0040] In this embodiment, in order to better analyze the absorption of incident light by the high temperature resistant lower layer and the anti-reflection upper layer of the structure, the field distribution diagram at the resonance absorption peak is analyzed. Figure 3As shown, it can be clearly seen that for the incident light at the resonance absorption peak, its electric field is mainly distributed in the anti-reflection layer formed by the top metal Ge. When it reaches the high-temperature resistant lower layer formed by the metal Mo below, the field distribution begins to decrease significantly. At the bottom, the field distribution is almost 0. Since the imaginary part of the relative dielectric constant of metal Ge in the infrared band is almost 0, the loss of incident light is almost 0. Therefore, in the present invention, the absorption of incident light by the structure is mainly the high absorption of the high-temperature resistant lower layer formed by the metal Mo below and the anti-reflection absorption of the anti-reflection layer formed by the metal Ge above.

[0041] In this embodiment, through simulation design and structural optimization, an infrared stealth material formed by a high-temperature resistant lower layer and an anti-reflective upper layer that meets the expected infrared stealth function is theoretically obtained. On the basis of the existing structural parameters, the corresponding experimental samples of the present invention are prepared by a vacuum magnetron sputtering coating machine. The metal Mo and metal Ge are deposited in sequence on the silicon wafer. Among them, the sputtering power of metal Mo is 100W, the working pressure is 0.5Pa, and the deposition rate is about 10nm / min; the sputtering power of dielectric Ge is 150W, the working pressure is 0.5Pa, and the deposition rate is about 20.5nm / min. At the same time, a cross-sectional view of the sample is obtained by a scanning electron microscope (SEM), see Figure 4 shown.

[0042] The absorption spectrum of the prepared sample in the infrared band was measured by infrared Fourier spectrometer and Figure 2 For comparison, see the absorption spectra obtained by simulation calculation in Figure 5 As shown in the figure, the absorption spectrum of the experimental sample shows that the difference between the absorption spectrum of the sample and the theoretical absorption spectrum obtained in the simulation is small. Due to certain problems in the coating process and sample thickness measurement, such as the certain deviation in the material sputtering rate measured in the early stage and the low precision of the thickness measurement equipment, there is a certain deviation between the thickness of the corresponding layer of the actual sample and the thickness used in the simulation, which in turn leads to a certain difference between the calculated and theoretical absorption spectra. This can be achieved by optimizing the coating process to make the experiment more accurate, thereby further reducing the difference between the experimental results and the simulation. At the same time, this result of this embodiment fully demonstrates the application prospects of the new infrared stealth material based on high-temperature resistant metal Mo in infrared stealth.

[0043] In summary, the double-layer infrared stealth material based on high-temperature resistant metal of the present invention includes a high-temperature resistant lower layer and an anti-reflection upper layer; the high-temperature resistant lower layer uses metal Mo; the anti-reflection upper layer uses metal Ge; the thickness of the high-temperature resistant lower layer is greater than the skin depth of the incident light; the thickness of the anti-reflection upper layer is adjusted according to the resonance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer. During the preparation process, the absorptivity, refractive index, and transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer are calculated using a transmission matrix combined with simulation software to obtain the absorption spectrum of the structure under normal incidence. The absorption spectrum is used to characterize the relationship between the absorptivity of the structure and the wavelength of the incident light; the thickness of the high-temperature resistant lower layer and the anti-reflection upper layer of the structure is adjusted, and the absorption spectrum of the structure at the set thickness is calculated to obtain the optimized thickness of the structure. The optimized structure is then prepared by magnetron sputtering and electron beam evaporation. The present invention utilizes Mo, a metal with excellent infrared properties, high temperature resistance, and good thermal stability, to design a new infrared stealth material based on high-temperature-resistant Mo. This replaces traditional low-melting-point precious metals such as Au and Ag, resulting in improved thermal stability and enabling the stealth material to achieve infrared stealth at higher background temperatures. The stealth material structure consists of two Mo / Ge films. The absorptivity of the two-layer film structure is calculated using a transmission matrix to obtain an absorption spectrum at normal incidence. Experimental results show that the present invention can well match the atmospheric infrared window, exhibiting high absorptivity in the non-atmospheric window band and relatively low absorptivity in the infrared window band with high atmospheric transmittance. This material effectively meets the practical requirements for selective infrared radiation stealth. Furthermore, the material has a simple structure and is easy to prepare. The optimized structure was prepared by magnetron sputtering and other methods, and the infrared absorption spectrum of the obtained sample was measured. The measured results are consistent with those obtained from theoretical calculations, demonstrating the feasibility of the present invention in practical applications, especially its practical significance in achieving stealth in high-temperature environments.

[0044] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. Double-layer structure infrared stealth material based on high temperature resistant metal, characterized by: It includes a high temperature resistant lower layer and an anti-reflection upper layer; the high temperature resistant lower layer is made of metal Mo; the anti-reflection upper layer is made of metal Ge; The thickness of the high temperature resistant lower layer is greater than the skin depth of the incident light; The thickness of the anti-reflection upper layer is adjusted according to the resonance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer.

2. The double-layer structure infrared stealth material based on high temperature resistant metal according to claim 1 is characterized in that: The thickness H1 of the high temperature resistant lower layer is greater than the incident plane wave skin depth of the incident light, so that the transmittance of the structure formed by the high temperature resistant lower layer and the anti-reflection upper layer approaches zero.

3. The double-layer infrared stealth material based on high-temperature resistant metal according to claim 1 is characterized in that: The calculation formula for the absorptivity of the structure formed by the high temperature resistant lower layer and the anti-reflection upper layer is: A=1-TR Where R, T and A are the reflectivity, transmittance and absorptivity of the structure, respectively.

4. A method for preparing a double-layer infrared stealth material based on high-temperature resistant metal according to any one of claims 1 to 3, characterized in that: The following steps are involved: The absorptivity, refractive index, and transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer are calculated using a transmission matrix combined with simulation software to obtain an absorption spectrum of the structure under normal incidence. The absorption spectrum is used to characterize the relationship between the absorptivity of the structure and the wavelength of the incident light. The thickness of the high-temperature resistant lower layer and the anti-reflection upper layer of the structure is adjusted, the absorption spectrum of the structure at the set thickness is calculated, and the optimized thickness of the structure is obtained. The optimized structure is prepared by magnetron sputtering and electron beam evaporation.

5. The method for preparing a double-layer infrared stealth material based on high-temperature resistant metal according to claim 4, characterized in that: In the process of calculating the absorptivity, refractive index and transmittance of the structure formed by the high-temperature resistant lower layer and the anti-reflection upper layer using the transmission matrix combined with simulation software, a plane wave with a wavelength range of 3 to 12 μm is defined as being vertically incident on the surface of the structure, and the left and right ends of the structure are set as periodic boundary conditions, and the upper and lower ends of the structure are set as port conditions.

6. The method for preparing a double-layer infrared stealth material based on high-temperature resistant metal according to claim 5, characterized in that: The thicknesses of the high-temperature resistant lower layer and the anti-reflection upper layer of the structure are adjusted to match the impedance of the structure with the impedance of air, so that the reflectivity of the structure is 0.

7. The method for preparing a double-layer infrared stealth material based on high-temperature resistant metal according to claim 6, characterized in that: The absorption rate of the structure in the atmospheric window is lower than the absorption rate of the structure in the non-atmospheric window.

8. The method for preparing a double-layer infrared stealth material based on high-temperature resistant metal according to claim 7, characterized in that: In the process of preparing the optimized structure by magnetron sputtering and electron beam evaporation, metal Mo and metal Ge are deposited on the silicon wafer in sequence; The sputtering power of metal Mo is 100W, the working pressure is 0.5Pa, and the deposition rate is 10nm / min; The sputtering power of metal Ge is 150 W, the working pressure is 0.5 Pa, and the deposition rate is 20.5 nm / min.

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