A multilayer film compatible with full infrared band invisibility and dual-band radiation heat dissipation

Abstract

The application provides a multilayer film compatible with full infrared band stealth and double-band radiation heat dissipation, comprising a substrate, a middle infrared selective emission layer, a short-wave infrared spectrum regulation layer and a near infrared antireflection layer, which meets the requirements that the emissivity of the short-wave infrared, middle-wave infrared and long-wave infrared bands is lower than 0.5, the reflectivity of the near infrared band is lower than 0.5, and the emissivity of the 2.5-3 mu m and 5-8 mu m non-atmospheric transparent window is greater than 0.5. The multilayer film of the application also has low reflectivity in the visible light band, and has visible light absorption type stealth capability. The multilayer film of the application has effective radiation heat dissipation heat management capability while realizing the stealth capability in the full infrared and visible bands, and can be widely applied in the fields of aviation, aerospace and the like.

Description

Technical Field

[0001] This invention belongs to the field of multi-band stealth technology, specifically relating to a multi-layer thin film that is compatible with both full-infrared stealth and dual-band radiation heat dissipation. Background Technology

[0002] Stealth technology refers to techniques that enable a target to remain undetected or reduce the likelihood of detection by an enemy's detection systems. In the optical band, depending on the detection wavelength, stealth technology can be categorized into visible light stealth, near-infrared stealth, short-wave infrared stealth, mid-wave infrared stealth, and long-wave infrared stealth. Currently, multi-band compatible stealth technology is becoming a research hotspot to counter the threat of advanced multi-band detection technologies. Simultaneously, stealth materials must also possess thermal management capabilities to reduce the target's thermal load.

[0003] The signal sources and stealth requirements for each band are as follows: 1. In the near-infrared (0.78–1.4 μm) and visible light (400–780 nm) bands, the signal source is mainly reflected ambient light, including sunlight, moonlight, starlight, lamplight, lasers, etc. It is necessary to reduce the reflected signal from the target surface to enhance its stealth; the corresponding methods mainly include using transparent materials, high-absorption materials, and camouflage. 2. In the short-wave infrared (1.4–2.5 μm), mid-wave infrared (3–5 μm), and long-wave infrared (8–14 μm) bands, the signal source is mainly the thermal radiation of the target itself; it is necessary to suppress the radiation signal to achieve stealth; the corresponding methods mainly include reducing the temperature of the target surface and reducing the emissivity of the target surface.

[0004] The thermal management capability of stealth materials is mainly achieved through radiative heat dissipation through non-atmospheric transparent windows (i.e., non-infrared detection bands). These non-atmospheric transparent windows include the 2.5-3 μm and 5-8 μm bands.

[0005] Existing multi-band compatible stealth technologies mainly use multilayer dielectric films such as infrared stealth films with spectrally selective low emissivity and their preparation methods (CN104865618A), multilayer metal-dielectric films such as metal-dielectric type spectrally selective multi-band stealth films and their preparation methods (CN112346162A), and two-dimensional grating structures such as optical band multifunctional stealth materials based on selective absorption and radiation nanostructures (CN110703369B). The shortcomings of the existing technologies are: (1) they are not compatible with short-wave infrared stealth and cannot hide the thermal radiation signals of short-wave infrared bands; (2) they do not consider stealth for broadband illumination sources in the near-infrared band and only target a few discrete laser wavelengths; (3) they do not utilize 2.5-3μm non-atmospheric transparent windows for radiation heat dissipation; (4) multilayer dielectric films have the problem of a large number of layers and a large thickness; (5) two-dimensional grating structures have the problem of relying on photolithography technology and having high preparation costs.

[0006] In summary, existing multi-band stealth technologies cannot cover all bands, including visible light, near-infrared, short-wave infrared, mid-wave infrared, and long-wave infrared, and cannot fully utilize two non-atmospheric transparent windows for radiative heat dissipation. Therefore, how to design a stealth material that is easy to fabricate and can achieve stealth in both the full infrared and visible bands as well as dual-band radiative heat dissipation is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides a multilayer thin film that is compatible with full infrared band stealth and dual-band radiative heat dissipation. This thin film can achieve stealth in the visible light, near infrared, short-wave infrared, mid-wave infrared and long-wave infrared bands, and is compatible with radiative heat dissipation through two non-atmospheric transparent windows.

[0008] A multilayer thin film compatible with full-infrared stealth and dual-band radiation heat dissipation includes, from the inside out, a mid-infrared selective emission layer, a short-wave infrared spectral modulation layer, and a near-infrared antireflection layer; it satisfies:

[0009] The infrared emissivity in the 1.4-2.5μm, 3-5μm and 8-14μm bands is less than 0.5;

[0010] The infrared reflectance for the 0.78-1.4μm range is less than 0.5;

[0011] The infrared emissivity in the 2.5-3μm and 5-8μm bands is higher than 0.5.

[0012] In the aforementioned multilayer thin film structure, the mid-infrared selective emission layer is used to achieve low emissivity stealth in the mid-infrared (3-5μm) and long-infrared (8-14μm) bands and high emissivity radiative heat dissipation in the 5-8μm band; the short-infrared spectral modulation layer is used to achieve low emissivity stealth in the short-infrared (1.4-2.5μm) band and high emissivity radiative heat dissipation in the 2.5-3μm band; and the near-infrared antireflection layer is used to reduce the reflectivity in the near-infrared (0.78-1.4μm) and visible (0.4-0.78μm) bands, thereby achieving absorption-type stealth in the near-infrared and visible bands.

[0013] Preferably, the mid-infrared selective emission layer is composed of a lossy dielectric layer and a metal reflective layer, wherein the lossy dielectric layer is disposed close to the short-wave infrared spectral modulation layer.

[0014] As a further preferred option, the material of the damaged dielectric layer is a germanium-antimony-tellurium alloy.

[0015] As a further preferred embodiment, the metal reflective layer material is one of platinum, chromium, nickel, tungsten, molybdenum, etc. Nickel is even more preferred.

[0016] As a further preferred option, the thickness of the germanium-antimony-tellurium alloy is 200–300 nm.

[0017] As a further preferred embodiment, the thickness of the metal reflective layer is greater than 50 nm. More preferably, the thickness of the metal reflective layer is 90–150 nm.

[0018] Preferably, the short-wave infrared spectral modulation layer has a multi-layer structure, consisting of alternating layers of various high and low refractive index dielectric materials.

[0019] As a further preferred option, the high refractive index medium material is selected from one or more of germanium, silicon, tellurium, etc. Germanium is even more preferred.

[0020] As a further preferred option, the low refractive index material is selected from one or more of the following: magnesium fluoride, ytterbium fluoride, calcium fluoride, barium fluoride, silicon dioxide, aluminum oxide, hafnium oxide, zinc oxide, zinc sulfide, and zinc selenide.

[0021] Furthermore, fluorides include, but are not limited to, magnesium fluoride, ytterbium fluoride, calcium fluoride, and barium fluoride.

[0022] Furthermore, oxides include, but are not limited to, silicon dioxide, aluminum oxide, hafnium oxide, zinc oxide, etc.

[0023] Furthermore, sulfides include, but are not limited to, zinc sulfide.

[0024] As a further preferred option, low refractive index materials are zinc sulfide and aluminum oxide.

[0025] As a further preferred option, the thickness of the high refractive index dielectric material layer is 200–400 nm.

[0026] As a further preferred option, the thickness of the low-refractive-index dielectric material layer is 150–600 nm.

[0027] As a further preferred embodiment, the short-wave infrared spectral modulation layer is composed of alternating layers of three dielectric materials with different refractive indices. In this technical solution, the short-wave infrared spectral modulation layer is composed of alternating layers of high- and low-refractive-index dielectric materials, and there can be two types of high- or low-refractive-index materials; taking two types of low-refractive-index materials as an example, the low-refractive-index dielectric material layers that are alternately stacked with the high-refractive-index dielectric material layers are made of two different types of refractive indices.

[0028] Furthermore, the three media materials with different refractive indices are germanium, aluminum oxide, and zinc sulfide.

[0029] Furthermore, the germanium layer has a thickness of 200-400 nm; the aluminum oxide layer has a thickness of 150-400 nm; and the zinc sulfide layer has a thickness of 450-600 nm.

[0030] Preferably, the total number of layers in the short-wave infrared spectral modulation layer is 4 to 8.

[0031] Preferably, the near-infrared antireflective layer material is one or more of the following: magnesium fluoride, ytterbium fluoride, calcium fluoride, barium fluoride, silicon dioxide, aluminum oxide, hafnium oxide, zinc oxide, zinc sulfide, and zinc selenide. Aluminum oxide is more preferably preferred.

[0032] Preferably, the thickness of the near-infrared reflective layer is less than 150 nm. More preferably, it is 50–100 nm.

[0033] Preferably, the multilayer film further includes a substrate disposed on the side of the mid-infrared selective emission layer away from the short-wave infrared spectral modulation layer for mechanical support.

[0034] As a further preferred embodiment, the substrate material is a solid or flexible material, including but not limited to one or more of silicon, silicon dioxide, polyimide (PI), polyethylene (PE), and polyetherimide (PEI). Silicon is even more preferred.

[0035] As a further preferred option, the thickness of the substrate can be set according to actual needs.

[0036] For the lossy dielectric layer in the mid-infrared selective emission layer, when the material thickness d, refractive index n, and effective wavelength λ satisfy the following relationship, an approximately perfect absorption peak can be formed at the effective wavelength:

[0037] nd = λ / 4

[0038] The multilayer thin film of this invention achieves stealth in the full infrared and visible light bands, requiring the following conditions: low emissivity in the 1.4-2.5μm short-wave infrared band, 3-5μm mid-wave infrared band, and 8-14μm long-wave infrared band to suppress its own thermal radiation signal; high absorptivity (i.e., low reflectivity) in the 0.78-1.4μm near-infrared band and 400-780nm visible light band to reduce reflection signals from ambient light sources; and high emissivity in the two non-atmospheric transparent windows at 2.5-3μm and 5-8μm to achieve dual-band radiative heat dissipation. The multilayer thin film of this invention achieves low emissivity in the short-wave infrared, mid-wave infrared, and long-wave infrared bands and low reflectivity in the near-infrared and visible light bands, thus achieving stealth; simultaneously, it also achieves radiative heat dissipation through the 2.5-3μm and 5-8μm non-atmospheric transparent windows. The fabrication process is simple and can meet the requirements for multi-band stealth in the full infrared and visible light bands, as well as thermal management requirements at high temperatures.

[0039] This invention relates to a multilayer thin film compatible with both full-infrared stealth and dual-band radiative heat dissipation. It comprises a substrate, a mid-infrared selective emission layer, a short-infrared spectral modulation layer, and a near-infrared antireflection layer. The film satisfies the following requirements: emissivity below 0.5 in the short-infrared, mid-infrared, and long-infrared bands; reflectivity below 0.5 in the near-infrared band; and emissivity greater than 0.5 for the 2.5-3 μm and 5-8 μm non-atmospheric transparent windows. The multilayer thin film also exhibits low reflectivity in the visible light band, providing visible light absorption stealth capability. This multilayer thin film achieves stealth capabilities in both the full infrared and visible light bands while also possessing effective radiative heat dissipation thermal management capabilities, making it widely applicable in aerospace and other fields.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This invention relates to a multilayer thin film that combines full-infrared stealth and dual-band radiative heat dissipation. It significantly reduces thermal radiation signals in the short-wave infrared, mid-wave infrared, and long-wave infrared bands, exhibiting strong resistance to thermal detectors. It also reduces reflection signals in the near-infrared and visible bands, providing protection against passive visible-near-infrared detectors and active searchlighting devices. Furthermore, this multilayer thin film achieves dual-band radiative heat dissipation through two non-atmospheric transparent windows, providing effective thermal management capabilities and making it widely applicable in aviation, aerospace, and other fields. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the multilayer thin film in Embodiment 1 of the present invention;

[0043] Figure 2 The simulated and experimental emissivity spectra of the multilayer thin film in Example 1 of this invention are shown.

[0044] Figure 3 This illustrates the relationship between the signal intensity of the multilayer thin film in Embodiment 1 of the present invention, measured by a short-wave infrared camera, and the actual temperature.

[0045] Figure 4 This is the relationship between the radiation temperature of the multilayer thin film in Embodiment 1 of the present invention, measured by a mid-wave infrared camera, and the actual temperature.

[0046] Figure 5 This is the relationship between the radiation temperature of the multilayer thin film in Embodiment 1 of the present invention, measured by a long-wave infrared camera, and the actual temperature.

[0047] Figure 6 This is a comparison of the equilibrium temperature of the multilayer thin film in Embodiment 1 of the present invention under different heating powers with that of traditional infrared stealth materials (chromium film). Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0049] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0050] This invention provides a multilayer thin film that is compatible with both full-infrared stealth and dual-band radiation heat dissipation, comprising: a substrate, a mid-infrared selective emission layer, a short-wave infrared spectral modulation layer, and a near-infrared anti-reflection layer sequentially disposed on the surface of the substrate;

[0051] The substrate layer, serving as a mechanical support, can have its thickness adjusted as needed. Specifically, the substrate material can be a solid or flexible material. Preferably, the substrate material is silicon.

[0052] A mid-infrared selective emission layer is used to achieve low emissivity in the mid-infrared (3-5μm) and long-infrared (8-14μm) bands and high emissivity in the 5-8μm band. Specifically, the mid-infrared selective emission layer consists of a lossy dielectric layer and a metal reflective layer. Preferably, the lossy dielectric layer is made of germanium-antimony-tellurium alloy with a thickness of 200-300nm; the metal reflective layer is made of nickel with a thickness greater than 50nm.

[0053] A short-wave infrared spectral modulation layer is used to achieve low emissivity in the short-wave infrared (1.4-2.5 μm) band and high emissivity in the 2.5-3 μm band. Specifically, the short-wave infrared spectral modulation layer is a multilayer structure composed of alternating layers of dielectric materials with different refractive indices. Preferably, the short-wave infrared spectral modulation layer is a multilayer structure composed of alternating layers of dielectric materials with three different refractive indices. Preferably, the three dielectric materials are germanium, alumina, and zinc sulfide; the thickness of the germanium layer is 200-400 nm, the thickness of the alumina layer is 150-400 nm, and the thickness of the zinc sulfide layer is 450-600 nm.

[0054] A near-infrared antireflection layer is used to reduce reflectivity in the near-infrared band; specifically, the near-infrared antireflection layer material is a dielectric material. Preferably, the dielectric material is alumina; the alumina layer thickness is less than 150 nm.

[0055] The present invention will be further described below with reference to specific embodiments.

[0056] Example 1

[0057] like Figure 1As shown, a multilayer thin film compatible with full-infrared stealth and dual-band radiation heat dissipation includes a substrate, a mid-infrared selective emission layer, a short-wave infrared spectral modulation layer and a near-infrared anti-reflection layer arranged sequentially from bottom to top (or from inside to outside).

[0058] The substrate material is silicon; the mid-infrared selective emission layer has a two-layer structure, consisting of a 120nm thick nickel layer and a 220nm thick germanium-antimony-tellurium alloy layer from bottom to top; the short-wave infrared spectral modulation layer has a four-layer structure, consisting of a 510nm thick zinc sulfide layer, a 250nm thick germanium layer, a 240nm thick aluminum oxide layer, and a 350nm thick germanium layer from bottom to top; and the near-infrared antireflection layer has a 65nm thick aluminum oxide layer.

[0059] The emissivity spectrum of the aforementioned multilayer thin film, which is compatible with both full-infrared stealth and dual-band radiative heat dissipation, is as follows: Figure 2 As shown. By Figure 2 As can be seen, the aforementioned multilayer thin films achieve low emissivity stealth in the short-wave infrared, mid-wave infrared, and long-wave infrared bands, absorption-based stealth in the near-infrared and visible bands, and high emissivity heat dissipation in the 2.5-3μm and 5-8μm bands. Specifically, the average emissivity is 0.275 in the 1.4-2.5μm short-wave infrared band; 0.102 in the 3-5μm mid-wave infrared band; and 0.173 in the 8-14μm long-wave infrared band. The average reflectivity (reflectivity = 1 - emissivity) is 0.476 in the 0.78-1.4μm near-infrared band; and 0.156 in the 400-780nm visible light band. The average emissivity is 0.758 in the 2.5-3μm band and 0.563 in the 5-8μm band.

[0060] The relationship between the signal intensity of the aforementioned multilayer thin film, which is compatible with both full-infrared stealth and dual-band radiative heat dissipation, and the actual temperature, as measured by a short-wave infrared camera, is as follows: Figure 3 As shown. By Figure 3 As can be seen, the signal strength of the multilayer thin film in this embodiment is significantly lower than that of the blackbody. At an actual temperature of 200°C, the signal strength of the multilayer thin film in this embodiment decreases by 39.3%.

[0061] The relationship between the radiation temperature of the multilayer thin film in this embodiment, measured by a mid-wave infrared camera, and the actual temperature is as follows: Figure 4 As shown. By Figure 4 It can be seen that the radiation temperature of the multilayer thin film in this embodiment is significantly lower than its actual temperature. When the actual temperature is 200°C, its radiation temperature is only 87.2°C.

[0062] The relationship between the radiation temperature of the multilayer thin film in this embodiment, measured by a long-wave infrared camera, and the actual temperature is as follows: Figure 5As shown. By Figure 5 It can be seen that the radiation temperature of the multilayer thin film in this embodiment is significantly lower than its actual temperature. When the actual temperature is 200°C, its radiation temperature is only 91.7°C.

[0063] The radiative heat dissipation capability of the multilayer thin film in this embodiment is demonstrated as follows: Figure 6 As shown. The macroscopic shape and size of the multilayer thin film sample is a 4-inch disk, and the selected conventional infrared stealth material is a chromium film (240nm thick) of the same macroscopic shape and size. The heating device is an electric heating element connected to a DC power source and placed on insulating foam, and the temperature measuring device is a thermocouple in contact with the sample or the surface of the chromium film. The heating power was set from low to high, and the surface temperatures of the multilayer thin film sample and the chromium film in this embodiment when they reached thermal equilibrium were recorded respectively. The results are shown below. Figure 6 As shown. Under the same heating power, the temperature of the multilayer thin film sample proposed in this invention is lower than that of conventional low-emissivity surface materials. For example, when the heating power is 20W, the actual surface temperature of the sample (174.5℃) is as low as 14.4℃ lower than that of the chromium film (188.9℃). At high temperatures, the designed structure exhibits superior radiative heat dissipation thermal management characteristics.

[0064] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multilayer thin film compatible with both full-infrared band stealth and dual-band radiative heat dissipation, characterized in that, It includes, from the inside out, a mid-infrared selective emission layer, a short-wave infrared spectral modulation layer, and a near-infrared anti-reflection layer; The mid-infrared selective emission layer has a two-layer structure, consisting of a 120nm thick nickel layer and a 220nm thick germanium-antimony-tellurium alloy layer from bottom to top; the short-wave infrared spectral modulation layer has a four-layer structure, consisting of a 510nm thick zinc sulfide layer, a 250nm thick germanium layer, a 240nm thick aluminum oxide layer, and a 350nm thick germanium layer from bottom to top; and the near-infrared antireflection layer has a 65nm thick aluminum oxide layer. It satisfies: The infrared emissivity in the 1.4-2.5μm, 3-5μm and 8-14μm bands is less than 0.5; The infrared reflectance for the 0.78-1.4μm range is less than 0.5; The infrared emissivity in the 2.5-3μm and 5-8μm bands is higher than 0.5.

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