Multispectral camouflage infrared wavelength selective film and method of making same

Abstract

The application provides a multispectral camouflage infrared wavelength selection film and a preparation method thereof, and belongs to the technical field of spectral thermal radiation management, and comprises the following steps: according to the optical constant of a film material in a 3-25 mu m wave band, a material with directional emission in an 8-14 mu m wave band is selected as a directional emission layer material; the directional emission layer material is combined with a lossless dielectric material and a metal material to construct a cascaded Fabry-Perot resonant cavity structure; according to the arrangement order and the optical constant of each layer film, the thickness of each layer film is used as an optimization variable, an optimization algorithm with a quality factor function as a judgment basis is used for iterative calculation, and the optimal thickness of each layer film is obtained; according to the multi-layer composite film structure and the optimal thickness of each layer film, a magnetron sputtering process is used to deposit each layer film material on a substrate, and the multispectral camouflage infrared wavelength selection film is prepared. The scheme improves the optimization efficiency of the film layer, and realizes efficient thermal management while maintaining the multispectral camouflage performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of multi-layer film structure design and broadband spectral thermal radiation management, and particularly relates to a multi-spectral camouflage infrared wavelength selection film and a preparation method thereof. BACKGROUND

[0002] With the rapid development of infrared detection technology from single-band detection (such as mid-infrared 3-5 μm (MWIR) and long-wavelength infrared 8-14 μm (LWIR)) to multi-spectral band combination detection, higher requirements are put forward for infrared camouflage capability. The traditional camouflage strategy mainly relies on the use of low-emissivity materials in a single band (such as mid-infrared 3-5 μm or long-wavelength infrared 8-14 μm) to hide the target, which is difficult to achieve comprehensive protection in a multi-spectral detection environment. More seriously, low-emissivity design can significantly inhibit the heat dissipation capability of the target, leading to heat accumulation and causing thermal instability problems, thereby increasing the risk of being detected in continuous observation.

[0003] In recent years, radiation cooling films with spectral selective regulation capability are considered as a feasible path to solve the above-mentioned contradiction, which can achieve infrared camouflage while enhancing heat dissipation. However, existing researches mostly focus on the mid-infrared and long-wavelength infrared atmospheric windows, ignoring the potential of the very long-wavelength infrared band (VLWIR, 14-25 μm) in thermal management. For high-temperature platforms (such as aircraft engine nozzles with a temperature of about 950 K and exhaust pipes with a temperature of about 740 K), the MWIR / LWIR low-emissivity strategy is mainly used to suppress the radiation signal, but in platforms with relatively low temperatures (such as ship chimneys with a temperature of about 680 K), how to utilize the VLWIR band to achieve synergistic regulation of efficient radiation heat dissipation and infrared camouflage is still lacking of systematic research, thereby restricting the overall improvement of full-band infrared stealth and heat dissipation performance. Moreover, the optimization process of the current multi-layer film structure mostly relies on trial and error or local parameter scanning, lacking of unified and operable optical-thermal synergistic design basis, resulting in low structure optimization efficiency, and the results of different studies are difficult to effectively compare and analyze, and the problem of considering both thermal radiation management and mechanical protection is ignored.

[0004] Therefore, it is urgent to provide a multi-spectral camouflage infrared wavelength selection film and a preparation method thereof. SUMMARY

[0005] The present application provides a multi-spectral camouflage infrared wavelength selection film and a preparation method thereof, which can solve the problems of insufficient multi-spectral band camouflage and heat dissipation performance, poor mechanical performance, and low optimization efficiency of multi-layer film structure in existing infrared camouflage technology.

[0006] In a first aspect, the present application provides a preparation method of a multi-spectral camouflage infrared wavelength selection film, the preparation method comprising:

[0007] obtain optical constants of different thin film materials in a 3-25μm waveband range, and screen thin film materials with directional emission in an 8-14μm waveband as the directional emission layer material based on preset screening conditions;

[0008] combine the screened directional emission layer material with lossless medium material and metal material to construct a cascaded Fabry-Perot resonant cavity structure to form a multilayer composite film structure;

[0009] According to the arrangement order and optical constants of each layer film in the multilayer composite film structure, the optimal thickness of each layer film is obtained by using an optimization algorithm with the constructed quality factor function as the basis for judgment for iterative calculation until the quality factor function value meets the convergence condition; wherein the quality factor function is constructed according to the camouflage requirements in different target wavebands, and the target wavebands include 3-5μm, 5-8μm, 8-14μm and 14-25μm;

[0010] According to the multilayer composite film structure and the optimal thickness of each layer film, the multiband camouflage infrared wavelength selective film is prepared by sequentially depositing each layer film material on the substrate using a magnetron sputtering process.

[0011] Preferably, the optical constants include refractive index and extinction coefficient.

[0012] Preferably, the preset screening conditions are that the intersection point of the refractive index curve and the extinction coefficient curve is located in the 8-14μm waveband range, the extinction coefficient in the 3-5μm waveband range tends to 0, and the peak value of the extinction coefficient curve in the 14-25μm waveband range is not less than 0.5.

[0013] Preferably, the directional emission layer material is at least one of Al2O3, SiO, SiO2, AlN or TiO2.

[0014] Preferably, the lossless medium material is Ge material, and the cascaded Fabry-Perot resonant cavity structure includes at least two resonant cavities composed of Ge material with different thicknesses.

[0015] Preferably, the metal material is Mo or Ta, which is used to realize high emissivity in the 5-8μm waveband.

[0016] Preferably, the optimal thickness of each layer film is determined by the following way:

[0017] The thickness of each layer film is used as an optimization variable, and the arrangement order and optical constants of each layer film in the multilayer composite film structure are input into a multi-physics field simulation software to iteratively calculate the absorptivity of each layer film at different angles in the 3-25μm waveband range.

[0018] In each iteration, the quality factor function value is calculated according to the absorption of each layer film at different angles in the 3-25 μm wave band, and the thickness of each layer film is adjusted inversely through the quality factor function until the calculated quality factor function value is minimum, so as to output the optimal thickness of each layer film.

[0019] Preferably, the quality factor function F min The quality factor function F is determined by the following formula:

[0020]

[0021] In the formula, A(λ) is the integral difference between the actual emissivity and the target emissivity in the spectral range of 3-25 μm wave band, the middle infrared wave band, the 5-8 μm wave band, the far infrared wave band and the super long infrared wave band, B(λ) is the emissivity weighted value at the center wavelength of the detector, 0.1 and 0.9 are the weighted coefficients of the integral difference between the actual emissivity and the target emissivity and the emissivity weighted value at the center wavelength, respectively, and α(λ) is the actual emissivity at the wavelength λ of the simulation output.

[0022] Preferably, the process parameters of the magnetron sputtering are as follows: the sputtering power is 80-130 W, the applied bias voltage is -110 V to -10 V, the sputtering gas pressure is 0.5-1 Pa, the sputtering time is 1-10 nm / min, and the rotation speed of the substrate is 10-15 rad / min.

[0023] In the second aspect, the embodiments of the present application also provide a multispectral camouflage infrared wavelength selection film prepared by the preparation method of any one of the first aspect.

[0024] Preferably, from the incident surface to the substrate direction, the infrared wavelength selection film comprises a first directional emission area, a first resonance area, a second directional emission area, a selective absorption area, a second resonance area and a reflection area in sequence; wherein: the first directional emission area and the second directional emission area each comprise at least two directional emission layers with different refractive indexes; the first resonance area and the second resonance area each comprise a Fabry-Perot resonant cavity composed of Ge; the selective absorption area comprises a coupling layer and a metal layer; and the reflection area comprises a reflection layer.

[0025] More preferably, from the direction of the incident surface to the substrate, the infrared wavelength selective film structure is as follows: the first layer is composed of Al2O3 or AlN, with a thickness of 150-250 nm or 120-320 nm; the second layer is composed of SiO or SiO2, with a thickness of 60-140 nm; the third layer is Ge, with a thickness of 550-750 nm; the fourth layer is composed of SiO or SiO2, with a thickness of 60-140 nm; the fifth layer is composed of TiO2 or Al2O3, with a thickness of 350-550 nm or 150-250 nm; the sixth layer is ZnS, with a thickness of 50-250 nm; the seventh layer is composed of Mo or Ta, with a thickness of 8-12 nm or 6-10 nm; the eighth layer is Ge, with a thickness of 250-400 nm; the ninth layer is TiO2, with a thickness of 200-400 nm; and the tenth layer is composed of Ag or Al, with a thickness of 150-250 nm.

[0026] Compared with the prior art, the present application has at least the following beneficial effects:

[0027] In the present application, first, materials with directional emission characteristics in the 8-14 μm wave band are screened as the directional emission layer based on the optical constants of thin film materials, then the screened directional emission layer material is combined with lossless dielectric material and metal material to construct a cascaded Fabry-Perot resonant cavity structure, and on the basis of determining the arrangement order and optical constants of the multi-layer composite film structure, the thickness of each layer is taken as the optimization variable, and an optimization algorithm based on the quality factor function criterion is used for iterative calculation. The optimization process combines simulation optimization with physical mechanism guidance, preliminarily determines the arrangement order and thickness of the key layer by analyzing the resonance condition of the Fabry-Perot resonant cavity, and in the iteration process, the different camouflage requirements in the 3-5 μm wave band, 5-8 μm wave band, 8-14 μm wave band and 14-25 μm wave band are comprehensively considered, the multi-objective optimization basis with the quality factor function as the core is constructed to finely adjust the resonant cavity structure and thickness until the convergence condition is met, so as to obtain the optimal thickness of each layer. This method combining physical mechanism with simulation optimization not only greatly improves the design efficiency, but also ensures that the optimization result can achieve the balance of multi-spectral band performance on the basis of conforming to the optical principle. Finally, the magnetron sputtering process is used to deposit the film materials on the substrate in sequence, so that the finally obtained infrared wavelength selective film not only maintains the multi-spectral camouflage performance, but also realizes efficient thermal management. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort.

[0029] Figure 1 Absorption graph of the ideal multispectral compatible structure provided by the embodiment of the present application; wherein the blue curve is the atmospheric transmittance, the orange curve is the normal incidence (0°) emissivity, and the black curve is the high-angle (80°) directional emissivity;

[0030] Figure 2 A fracture microstructure diagram of a multispectral camouflage infrared wavelength selection film provided by the embodiment of the present application;

[0031] Figure 3 A simulation emissivity and actual measurement emissivity curve diagram of a multispectral camouflage infrared wavelength selection film provided by the embodiment of the present application under different angles;

[0032] Figure 4 An infrared emissivity curve diagram of a multispectral camouflage infrared wavelength selection film provided by the embodiment of the present application in the 8~14 μm waveband;

[0033] Figure 5 A thermal radiation camouflage effect diagram of a multispectral camouflage infrared wavelength selection film provided by the embodiment of the present application under different temperatures;

[0034] Figure 6 A displacement change curve diagram of a multispectral camouflage infrared wavelength selection film provided by the embodiment of the present application under different loading forces in different regions;

[0035] Figure 7 A hardness and modulus diagram of a multispectral camouflage infrared wavelength selection film provided by the embodiment of the present application in different regions. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0037] As described previously, most of the existing researches focus on the mid-infrared and far-infrared atmospheric windows, ignoring the potential of the super-long wave infrared band in thermal management. Considering that the super-long wave infrared band is more matched with the radiation peak region of the low-temperature target, it has high emissivity characteristics in the non-atmospheric window, and can provide an additional heat dissipation path for platforms such as ships, but the related design theory and experimental verification are still blank.

[0038] Therefore, the embodiment of the present application provides a preparation method of a multispectral camouflage infrared wavelength selection film, and the preparation method comprises the following steps:

[0039] Optical constants of different film materials in a 3-25 μm wave band range are obtained, and a film material with directional emission in an 8-14 μm wave band is selected as a directional emission layer material based on a preset screening condition;

[0040] The directional emission layer material selected is combined with a lossless medium material and a metal material to construct a cascaded Fabry-Perot resonant cavity structure, so as to form a multilayer composite film structure;

[0041] According to the arrangement order and the optical constants of each layer film in the multilayer composite film structure, the optimal thickness of each layer film is obtained by iterative calculation of an optimization algorithm taking a quality factor function as a judgment basis, until the quality factor function value meets a convergence condition; wherein the quality factor function is constructed according to camouflage requirements in different target wave bands, and the target wave bands include 3-5 μm, 5-8 μm, 8-14 μm and 14-25 μm;

[0042] According to the multilayer composite film structure and the optimal thickness of each layer film, each layer film material is deposited on a substrate in sequence by using a magnetron sputtering process, so that the multispectral camouflage infrared wavelength selection film is prepared.

[0043] In the embodiment of the present application, first, a material with directional emission characteristics in an 8-14 μm wave band is selected as a directional emission layer based on the optical constants of the film material, then the directional emission layer material selected is combined with a lossless medium material and a metal material to construct a cascaded Fabry-Perot resonant cavity structure, and the optimal thickness of each layer film is obtained by iterative calculation of an optimization algorithm based on a quality factor function criterion, on the basis of determining the arrangement order and the optical constants of the multilayer composite film structure. The optimization process combines simulation optimization and physical mechanism guidance, preliminarily determines the arrangement order and the thickness of the key layer by analyzing the resonant condition of the Fabry-Perot resonant cavity, and in the iterative process, different camouflage requirements in a 3-5 μm wave band, a 5-8 μm wave band, an 8-14 μm wave band and a 14-25 μm wave band are considered comprehensively, the resonant cavity structure and the thickness are finely adjusted based on the multi-objective optimization basis taking the quality factor function as the core, until the convergence condition is met, so that the optimal thickness of each layer film is obtained. This method combining physical mechanism and simulation optimization not only greatly improves the design efficiency, but also ensures that the optimization result can achieve a balance of multispectral wave band performance on the basis of conforming to the optical principle. Finally, each layer film material is deposited on a substrate in sequence by using a magnetron sputtering process, so that the infrared wavelength selection film obtained finally not only maintains the multispectral camouflage performance, but also realizes efficient thermal management.

[0044] According to some preferred embodiments, the optical constants include an optical constant refractive index and an extinction coefficient; and the preset screening condition is that the intersection of the refractive index curve and the extinction coefficient curve is located in the 8-14 μm waveband range, the extinction coefficient in the 3-5 μm waveband range tends to 0, and the peak value of the extinction coefficient curve in the 14-25 μm waveband range is not less than 0.5.

[0045] According to some preferred embodiments, the directional emission layer material is at least one of Al2O3, SiO, SiO2, AlN or TiO2.

[0046] In order to achieve the camouflage requirement in the 8-14 μm waveband, in the embodiments of the present application, by analyzing the optical constants of different thin film materials, a double screening condition is set according to the optical constant refractive index n and the extinction coefficient k of different thin film materials, which requires that the intersection of the n and k curves is located in 8-14 μm, so as to utilize the strong dispersion and absorption characteristics of the material in this region to realize directional emission at different angles, and at the same time, it is required that k tends to 0 in the 3-5 μm range to ensure that the low emissivity requirement of this waveband is not affected, and the extinction coefficient in the 14-25 μm waveband range is relatively high to ensure sufficient intrinsic absorption and heat dissipation capacity; at the same time, on the basis of meeting the above optical properties, the mechanical properties of the material are further considered, and the thin film material with high mechanical properties is placed on the top layer of the thin film, so as to ensure the durability of the overall structure; this quantitative multi-dimensional screening method not only can improve the selection efficiency and accuracy of the thin film material, but also can lay a foundation for subsequent construction of a Fabry-Perot resonant cavity structure with excellent optical properties and mechanical stability.

[0047] According to some preferred embodiments, the lossless medium material is Ge material, the cascaded Fabry-Perot resonant cavity structure includes at least two resonant cavities composed of Ge materials with different thicknesses; and the metal material is Mo material with a wetting angle greater than 90°, which is used to realize high emissivity in the 5-8 μm waveband.

[0048] Considering the synergistic requirements of each waveband in multispectral camouflage and the preparation feasibility, in the embodiments of the present application, Ge material is selected as the lossless medium material, Mo material is selected as the metal material, and they are gradient combined according to the refractive index to form a cascaded Fabry-Perot resonant cavity together. The Mo material has a relatively high absorption rate in the 5-8 μm waveband, so as to ensure high emissivity (emissivity greater than 0.5) in the 5-8 μm waveband. In addition, the Mo material with a high wetting angle is selected to ensure the surface smoothness and density during the film forming process, so as to be conducive to ensuring the stability of the optical properties of the infrared wavelength selection thin film material and the repeatability of the process.

[0049] According to some preferred embodiments, the optimal thickness of each film layer is determined as follows:

[0050] The thickness of each film layer was used as the optimization variable, and the arrangement order and optical constants of each film layer in the multilayer composite film structure were input into the multiphysics simulation software to iteratively calculate the absorption rate of each film layer at different angles in the 3-25μm band.

[0051] In each iteration, the quality factor function value is calculated based on the absorption rate of each film at different angles in the 3-25μm band, and the thickness of each film is adjusted in reverse using the quality factor function until the calculated quality factor function value is minimized, so as to output the optimal thickness of each film.

[0052] In this embodiment of the invention, after determining the directional emission layer material, the non-destructive dielectric material, and the metallic material, in order to achieve multiple objectives—low emissivity in the 3-5 μm band, high directional emissivity in the 8-14 μm band, and high emissivity in the 14-25 μm band—a cascaded Fabry-Perot resonator structure is constructed based on physical mechanisms. This structure possesses wavelength selectivity, angle sensitivity, and broadband response capabilities, enabling the intrinsic properties of the material to be transformed into intelligent infrared camouflage performance. Then, based on this initial structure (including the arrangement order of each film layer and the thickness of key films), a geometric model of the multilayer thin film is established in multiphysics simulation software, and the optical constants (n, ...) of each material layer are accurately set. Given k) and the initial thickness, the emissivity of the multilayer thin film at different angles (e.g., 0°, 30°, 60°, 80°) in the 3-25μm band is simulated and calculated. The emissivity output from each simulation is input into the constructed quality factor function to quantify the gap between it and the target performance. The thickness of each layer is automatically adjusted iteratively through an optimization algorithm to find the optimal combination of thicknesses that minimizes the objective function value, thereby completing the precise design of the thin film structure.

[0053] According to some preferred embodiments, the quality factor function F min It is determined by the following formula:

[0054]

[0055] In the formula, such as Figure 1 As shown, A(λ) is the integral difference between the actual emissivity and the target emissivity in the mid-infrared band (3~5μm), RC band (5~8μm), far-infrared band (8-14μm), and ultra-long infrared band (14~25μm) within the 3~25μm spectral range; B(λ) is the emissivity weighted value at the center wavelength of the detector; 0.1 and 0.9 are the weighting coefficients for the integral difference between the actual emissivity and the target emissivity and the emissivity weighted value at the center wavelength, respectively; and α(λ) is the actual emissivity at the simulated output wavelength λ.

[0056] In the embodiment of the present application, based on the camouflage and heat dissipation requirements of different target wavebands of 3-5 μm, 5-8 μm, 8-14 μm and 14-25 μm, a quality factor function F min is proposed as the optimization method for judgment. The quality factor function is constructed by two sub-functions A(λ) and B(λ). The B(λ) function focuses on two key wavelength points of the mid-wave infrared (4 μm) and long-wave infrared (11 μm) of the detector center wavelength, and requires a very low emissivity to ensure the camouflage performance. The A(λ) function can ensure high emissivity of the material in the non-atmospheric window (5-8 μm and 14-25 μm) on the basis of meeting the camouflage performance, so as to efficiently radiate heat. Further, according to the optimization target, specific weight coefficients are given to the A(λ) and B(λ) functions, so as to improve the heat dissipation efficiency as much as possible on the premise of priority to ensure the camouflage performance. In this way, the above quality factor function formula can balance the total emissivity of the detector center wavelength and different wavebands, so as to quickly and accurately develop a multi-layer infrared thermal radiation camouflage film integrating the functions of wavelength selection emission, directional heat radiation and mechanical protection, and simultaneously realize high-temperature infrared camouflage and excellent mechanical protection performance in the wide waveband of 3-25 μm.

[0057] According to some preferred embodiments, the process parameters of the magnetron sputtering are as follows: the sputtering power is 80-130 W (for example, it can be 80 W, 90 W, 100 W, 110 W, 120 W or 130 W), the applied bias voltage is -110 V to -10 V (for example, it can be -110 V, -100 V, -80 V, -50 V, -30 V, -20 V or -10 V), the sputtering gas pressure is 0.5-1 Pa (for example, it can be 0.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa or 1 Pa), the sputtering time is 1-10 nm / min (for example, it can be 1 nm / min, 1.2 nm / min, 1.3 nm / min, 1.4 nm / min, 1.8 nm / min, 2.5 nm / min, 3 nm / min, 4 nm / min, 5 nm / min, 6.6 nm / min, 8 nm / min, 8.5 nm / min, 9 nm / min or 10 nm / min), and the rotation speed of the substrate is 10-15 rad / min (for example, it can be 10 rad / min, 11 rad / min, 12 rad / min, 13 rad / min, 14 rad / min or 15 rad / min).

[0058] For different film material layers, the process parameters used in the sputtering process are different. According to some specific embodiments, when the film material is Al2O3, the target material is Al, the sputtering gas is argon and oxygen, the argon flow is 25-35sccm, the oxygen flow is 1-1.5sccm, the sputtering power is 95-105W, the applied bias voltage is-110 to-90V, the sputtering gas pressure is 0.8-1Pa, the sputtering time is 1-1.5nm / min, and the substrate rotation speed is 10-15rad / min; when the film material is SiO, Ge, ZnS, Mo or Ag, the target material is SiO, Ge, ZnS, Mo or Ag, that is, the film material is the same as the target material, the sputtering gas is argon, the argon flow is 25-35sccm, the sputtering power is 100-120W, the applied bias voltage is-30 to-20V, the sputtering gas pressure is 0.5-0.7Pa, the sputtering time is 1.0-8.5nm / min, and the substrate rotation speed is 10-15rad / min; when the film material is SiO2 or TiO2, the target material is SiO2 or Ti, the sputtering gas is argon and oxygen, the argon flow is 25-35sccm, the oxygen flow is 1.5-3sccm, the sputtering power is 120-130W, the applied bias voltage is-35 to-25V, the sputtering gas pressure is 0.5-0.7Pa, the sputtering time is 1.0-2.0nm / min, and the substrate rotation speed is 10-15rad / min;

[0059] Further, in the related art, most of the researches focus on the optical and thermal properties of infrared wavelength selection films, but when facing practical application environments such as sand erosion, rain erosion and the like, the mechanical properties and durability of the films are easily insufficient, and the thermal radiation control material is easily invalid in harsh working conditions. Therefore, in the embodiments of the present application, not only the mechanical properties are considered in the process of optimizing and selecting the film material, but also, on the basis of the optimized film structure and thickness, a bias voltage is applied in the process of magnetron sputtering, and the various process parameters are cooperatively controlled, so as to not only optimize the stress distribution between the film layers and improve the adhesion of the film to the substrate, but also facilitate the formation of a film layer with excellent mechanical properties and high density and uniformity, and finally effectively realize the coupling of high-temperature camouflage and mechanical protection of the infrared wavelength selection film, and ensure the long-term stability of the film in a complex environment.

[0060] The embodiments of the present application also provide a multi-spectrum camouflage infrared wavelength selection film prepared by the preparation method described in any one of the above.

[0061] According to some preferred embodiments, the infrared wavelength selective film comprises, in order from the incident surface to the substrate, a first directional emission region, a first resonance region, a second directional emission region, a selective absorption region, a second resonance region, and a reflection region; wherein: the first directional emission region and the second directional emission region each comprise at least two directional emission layers with different refractive indexes; the first resonance region and the second resonance region each comprise a Fabry-Perot resonance cavity composed of Ge; the selective absorption region comprises a coupling layer and a metal layer; and the reflection region comprises a reflection layer.

[0062] According to some preferred embodiments, the infrared wavelength selective film structure is as follows, in order from the incident surface to the substrate: a first layer composed of Al2O3 or AlN, when the first layer is Al2O3, the thickness is 150-250 nm (for example, it can be 150 nm, 200 nm, or 250 nm), and when the first layer is AlN, the thickness is 120-320 nm (for example, it can be 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, or 320 nm); a second layer composed of SiO or SiO2, the thickness is 60-140 nm (for example, it can be 60 nm, 80 nm, 100 nm, 120 nm, or 140 nm); a third layer of Ge, the thickness is 550-750 nm (for example, it can be 550 nm, 600 nm, 650 nm, 700 nm, or 750 nm); a fourth layer composed of SiO or SiO2, the thickness is 60-140 nm (for example, it can be 60 nm, 80 nm, 100 nm, 120 nm, or 140 nm); a fifth layer composed of TiO2 or Al2O3, when the fifth layer is TiO2, the thickness is 350-550 nm (for example, it can be 350 nm, 400 nm, 450 nm, 500 nm, or 550 nm), and when the fifth layer is Al2O3, the thickness is 150-250 nm (for example, it can be 150 nm, 200 nm, or 250 nm); a sixth layer of ZnS, the thickness is 50-250 nm (for example, it can be 50 nm, 100 nm, 150 nm, or 250 nm); a seventh layer composed of Mo or Ta, when the seventh layer is Mo, the thickness is 8-12 nm (for example, it can be 8 nm, 9 nm, 10 nm, 11 nm, or 12 nm), and when the seventh layer is Ta, the thickness is 6-10 nm (for example, it can be 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm); an eighth layer of Ge, the thickness is 250-400 nm (for example, it can be 250 nm, 300 nm, 350 nm, or 400 nm); a ninth layer of TiO2, the thickness is 200-400 nm (for example, it can be 200 nm, 300 nm, or 400 nm); and a tenth layer composed of Ag or Al, the thickness is 150-250 nm (for example, it can be 150 nm, 200 nm, or 250 nm).

[0063] In the embodiment of the present application, the cascade Fabry-Perot resonant cavity structure is combined with the simulation optimization mode, so that the above-mentioned multispectral camouflage infrared wavelength selection film realizes the synergy of multispectral band camouflage, heat dissipation and mechanical properties. The resonant cavity of the cascade structure is constructed by using Ge layers with different thicknesses and directional emission materials. By accurately controlling the optical thickness of each cavity, not only is the low-emissivity camouflage in the 3-5 μm band ensured, but also the high-emissivity heat dissipation performance in the 14-25 μm band is ensured, and the angle-sensitive directional emission performance in the 8-14 μm band is ensured. The Mo layer and the ZnS layer not only realize the high-emissivity characteristics in the 5-8 μm band as a selective absorption layer, but also form part of the reflector together with the dielectric layer to synergistically ensure the optimization performance of each band. In this way, based on the synergy design of the intrinsic characteristics of the material and the optical structure, the balance of multispectral camouflage, heat dissipation performance and mechanical properties is realized. At the same time, by combining the magnetron sputtering and bias process, not only the excellent optical performance of the film is ensured, but also the mechanical protection characteristics of high hardness, strong adhesion and corrosion resistance are realized, which provides reliable protection for the long-term stable operation of the film in harsh environments.

[0064] In order to more clearly illustrate the technical solutions and advantages of the present application, a multispectral camouflage infrared wavelength selection film and a preparation method thereof will be described in detail in the following embodiments.

[0065] Embodiment

[0066] The optimal film structure and thickness calculated by the above-mentioned simulation method are as follows from the incident surface to the substrate direction: the first layer is Al2O3, the thickness is 200 nm, the second layer is SiO, the thickness is 100 nm, the third layer is Ge, the thickness is 650 nm, the fourth layer is SiO2, the thickness is 100 nm, the fifth layer is TiO2, the thickness is 450 nm, the sixth layer is ZnS, the thickness is 50 nm, the seventh layer is Mo, the thickness is 10 nm, the eighth layer is Ge, the thickness is 350 nm, the ninth layer is TiO2, the thickness is 300 nm, and the tenth layer is Ag, the thickness is 200 nm.

[0067] The Si substrate is cleaned with 99.99% alcohol combined with ultrasonic wave for 15 min. According to the above-mentioned multilayer composite film structure and the thickness of each layer, the infrared wavelength selection film is prepared on the Si substrate by magnetron sputtering. The magnetron sputtering process parameters of different film layers are shown in Table 1:

[0068] Table 1

[0069]

[0070] The fracture microstructure of the above-mentioned prepared infrared wavelength selection film is as follows:Figure 2 As shown in Figure 2 It can be seen from the above that the infrared wavelength selective film prepared in the embodiment has good bonding between layers and is compact and uniform as a whole. The radiation performance of the infrared wavelength selective film was tested, and it was found that Figure 3 It can be seen from the above that the infrared wavelength selective film exhibits extremely low emissivity (0.07 and 0.15, respectively) in the mid-wave infrared (4 μm) and long-wave infrared (11 μm) at the center wavelength of the detector, thereby ensuring the camouflage performance; and high emissivity (0.9 and 0.95, respectively) is achieved in the non-atmospheric window (such as 5.6 μm and 22.5 μm). As shown in Figure 4 The emissivity of the infrared wavelength selective film in the long-wave infrared 8-14 μm band and at high angles (75°~85°) is >0.8, and further, as shown in Figure 5 In the 3-5 μm band, the surface temperature of the infrared wavelength selective film is significantly lower than 500℃ of the heating table, achieving full-angle camouflage effect; the infrared wavelength selective film has directional emission performance in the 8-14 μm band, and presents differential thermal characteristics at different observation angles. The surface temperature of the infrared wavelength selective film at each angle is lower than 120℃ of the heating table, and presents directional characteristics of low emission at low angles (<60°) and high emission at high angles (80°). At the same time, the mechanical properties of the infrared wavelength selective film were tested, and it was found from Figure 6 that the mechanical properties of the infrared wavelength selective film in each region are uniform, and from Figure 7 that the overall hardness of the infrared wavelength selective film is 14.8 GPa, which is increased by 48% compared with the overall hardness of the infrared wavelength selective film prepared by traditional processes (such as evaporation, electroplating, magnetron sputtering or atomic deposition), effectively realizing the coupling of high-temperature camouflage and mechanical protection.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent substitutions for some technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing a multispectral camouflage infrared wavelength selective film, characterized by, The preparation method comprises: obtaining optical constants of different thin film materials in a 3-25 μm wave band range, and screening thin film materials having directional emission in an 8-14 μm wave band as the directional emission layer material based on preset screening conditions; the optical constants include optical constant refractive index and extinction coefficient; the preset screening conditions are that an intersection of a refractive index curve and an extinction coefficient curve is located in the 8-14 μm wave band range, and the extinction coefficient in the 3-5 μm wave band range tends to 0, and a peak value of the extinction coefficient curve in the 14-25 μm wave band range is not less than 0.5; combining the directional emission layer material screened to obtain and lossless medium material and metal material to construct a cascaded Fabry-Perot resonant cavity structure to form a multilayer composite film structure; taking thicknesses of the layers of films as optimization variables, and inputting arrangement orders and optical constants of the layers of films in the multilayer composite film structure into a multi-physics field simulation software, and iteratively calculating absorptivities of the layers of films at different angles in the 3-25 μm wave band range; in each iteration, calculating a quality factor function value according to the absorptivities of the layers of films at different angles in the 3-25 μm wave band range, and inversely adjusting the thicknesses of the layers of films through the quality factor function until the quality factor function value calculated is minimum, to output optimal thicknesses of the layers of films; where the quality factor function F min is determined by the equation in the formula, A(λ) is an integral difference between actual emissivity and target emissivity in a 3-25 μm wave band spectral range, a middle infrared wave band, a 5-8 μm wave band, a far infrared wave band and an ultralong infrared wave band, B(λ) is an emissivity weighting value at a central wavelength of a detector, 0.1 and 0.9 are weighting coefficients of the integral difference between the actual emissivity and the target emissivity and the emissivity weighting value at the central wavelength respectively, and α(λ) is actual emissivity at a wavelength λ simulated and output; according to the multilayer composite film structure and the optimal thicknesses of the layers of films, using a magnetron sputtering process to sequentially deposit the layer of film materials on a substrate to prepare a multispectral camouflage infrared wavelength selective film; from an incident surface to a substrate direction, the infrared wavelength selective film sequentially comprises a first directional emission area, a first resonant area, a second directional emission area, a selective absorption area, a second resonant area and a reflection area; wherein: the first directional emission area and the second directional emission area each contain at least two directional emission layers of different refractive indexes; the first resonant area and the second resonant area each contain a Fabry-Perot resonant cavity composed of Ge; the selective absorption area contains a coupling layer and a metal layer; and the reflection area contains a reflection layer.

2. The production method according to claim 1, characterized by, The directional emission layer material is at least one of Al2O3, SiO, SiO2, AlN or TiO2.

3. The preparation method according to claim 1, characterized in that, The lossless medium material is Ge material, and the cascaded Fabry-Perot resonant cavity structure comprises at least two resonant cavities composed of Ge material of different thicknesses.

4. The method of claim 1, wherein, The metal material is Mo or Ta, and is used to realize high emissivity in a 5-8 μm wave band.

5. The preparation method according to claim 1, characterized in that, Process parameters of the magnetron sputtering are as follows: a sputtering power is 80-130 W, an applied bias is -110 V to -10 V, a sputtering gas pressure is 0.5-1 Pa, a sputtering time is 1-10 nm / min, and a rotation speed of a substrate is 10-15 rad / min.

6. A multispectral camouflage infrared wavelength selective film characterized by, Prepared by the method of any one of claims 1 to 5.

7. The multispectral camouflage infrared wavelength selective film of claim 6, wherein, In the direction from the incident surface to the substrate, the infrared wavelength selective film structure is as follows: the first layer is composed of Al2O3 or AlN, with a thickness of 150-250 nm or 120-320 nm; the second layer is composed of SiO or SiO2, with a thickness of 60-140 nm; the third layer is Ge, with a thickness of 550-750 nm; the fourth layer is composed of SiO or SiO2, with a thickness of 60-140 nm; the fifth layer is composed of TiO2 or Al2O3, with a thickness of 350-550 nm or 150-250 nm; the sixth layer is ZnS, with a thickness of 50-250 nm; the seventh layer is composed of Mo or Ta, with a thickness of 8-12 nm or 6-10 nm; the eighth layer is Ge, with a thickness of 250-400 nm; the ninth layer is TiO2, with a thickness of 200-400 nm; and the tenth layer is composed of Ag or Al, with a thickness of 150-250 nm.

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