Infrared Stealth Research Articles

3D Printing-Assisted Honeycomb-Structured Bricklike Aerogels Applied for Infrared Stealth with Good Thermal Management

3D Printing-Assisted Honeycomb-Structured Bricklike Aerogels Applied for Infrared Stealth with Good Thermal Management

Multifunctional-hierarchical flexible metasurface with simultaneous low infrared emissivity, broadband microwave absorption, and dynamic visible camouflage

Sophisticated multispectral detectors have made single-band camouflage materials ineffective, consequently leading to significant advancements in metasurfaces that possess both infrared (IR), radar, and visible stealth capabilities. However, the mutual constraints of stealth principles across different bands and the demand for environment-adaptive camouflage raise challenges to existing multispectral compatible stealth solutions. Here a multifunctional-hierarchical flexible metasurface (MHFM) including an infrared suppression layer (IRSL), three microwave absorbing layers (MAL), an environmental adaptation layer (EAL), and a total reflective sheet (TRS), was designed to simultaneously achieve IR, radar, and dynamic visible stealth. Unlike the direct stacking of functional layers in existing solutions, the EAL is directly integrated with the first MAL as a part of the absorbing structure. As a proof-of-concept, an MHFM sample with an area of 300 × 300 mm2 and a minimum linewidth of 20 µm is demonstrated. The excellent multispectral camouflage performance is verified in experiments, showing low infrared emissivity (0.229, covering the wavelength of 3∼14 µm), the high absorption efficiency of over 90% in 2.53∼34.56 GHz, and dynamic camouflage in both grassland and desert environments. Our work presents a new solution for adaptive visible camouflage and competitive IR-radar stealth that is prospectively applicable in complex environments.

Foldable sandwich fabric-based composites with thermal insulation and low emissivity for highly efficient infrared stealth

Fabric-based infrared (IR) stealth composites with thermal insulation and low emissivity are desirable for improving IR camouflage of military targets and thermal management of special environments. Therefore, a flexible and foldable composite fabric with a sandwich structure is delicate designed in this work aiming to realize dual-modes IR effects. Polyester fabric chemically plated with copper-nickel (Cu/Ni@PF) and aluminum foil (AF) are on the top and bottom, respectively, acting as low emissivity layers. The medium layer is constructed by silica aerogel microspheres (SAM) with thickeners and waterborne polyurethanes (WPU) functioned as thermal insulation. The thermal conductivity of as-prepared composite fabric is only 0.05904 W/(m·K). When the AF is heated to 70 °C, the introduction of the SAM in the medium layer with the thickness of 300 μm makes Cu/Ni@PF as top surface exhibit a obvious temperature difference of 11.7 °C, demonstrating excellent thermal insulation. The AF maintains a low emissivity of less than 0.2, and the emissivity of Cu/Ni@PF was also as low as 0.296 at 8–14 μm, which can effectively shield the IR signal. Thanks to the Cu/Ni@PF as the top surface, the radiation temperature displays only 36.3 °C when heated at 70 °C, which meaning the dramatic IR signal strength reduce. Therefore, this dual-modes flexible and foldable composite can be a potential candidate in the IR stealth fields.

High-performance long-wavelength infrared switchable stealth based on In3SbTe2 metasurface

Metasurface based on phase change material (PCM) for switchable thermal radiation is of great significance to the application of infrared (IR) stealth and thermal management in multi-scenario. However, the previously reported results based on GST and VO2 metasurface face the challenges of relatively low intrinsic loss in metallic state and weak stability, respectively. In this paper, we have designed a plasmonic metasurface thermal emitter (PMTE) based on the PCM of In3SbTe2 (IST), which can manage the thermal emissivity in the wavelength range of 5–14 μm as the IST changes from the amorphous to the crystalline state. For IST in the amorphous state, the PMTE's average emissivity in the wavelength ranges of 5–8 μm and 8–14 μm, are 0.22 and 0.44 respectively, which can be used for the long-wavelength IR (LWIR) stealth of object with low temperature in high-temperature environment. For IST in the crystalline state, the PMTE's average emissivity in the wavelength ranges of 5–8 μm and 8–14 μm, are 0.68 and 0.14 respectively, which can achieve radiative heat dissipation and LWIR stealth of object with high temperature in low-temperature environment. We displayed simulated infrared images of the PMTE in amorphous and crystalline states to demonstrate its switchable LWIR stealth at different temperatures. In addition, the radiative heat dissipation properties of the PMTE are discussed. Our proposed PMTE based on IST can be potentially applied to IR stealth and thermal management in different scenarios.

Unlocking versatile capabilities: Mixed-valence decavanadate aerogels for boosting radar, infrared, and thermal stealth

Multifunctional compatible stealth materials have emerged as the focal point of contemporary protection technology research and vanadium-based nanomaterials play a pivotal role in the development of advanced stealth materials. Here, a compatible stealth aerogel is successfully synthesized by employing mixed-valence decavanadate as the vanadium oxide (VOx) molecular model. Ultralight {VⅣVV9}/MXene aerogel (0.0429 g cm–3) exhibits exceptional radar stealth performance with a minimal reflection loss (RLmin) of −57.74 dB (99.9998% EMW absorption) and a significantly superior radar cross section reduction value of 26.77 dB m2. The aerogel's exceptional properties, including a low infrared (IR) emissivity (0.479) and a low thermal conductivity of (32.30 mW m–1 K–1), are crucial for enabling compatibility with IR and thermal stealth technologies. The presence of a mixed-valence polyoxovanadate cluster leads to an increase in the Schottky barrier and enhances magnetic properties, consequently boosting interfacial polarization and contributing to magnetic losses during electromagnetic wave (EMW) absorption. Consequently, altering the number of valence electrons significantly enhances the compatible stealth capabilities. These findings contribute significantly to our comprehension of how microstructure impacts EMW absorption processes and provide a basis for further research into the development of VOx-based compatible stealth materials.

Research Progress and Recent Advances in Development and Applications of Infrared Stealth Materials: A Comprehensive Review

AbstractIn modern war of “find and destroy,” hiding the target is one of the essential means to improve battlefield survivability of personnel, weapons, and equipment. Infrared stealth technology started to emerge when hiding in the visible light band could no longer meet the protection requirements. With the rapid development of infrared detection technology, infrared stealth materials are gradually diversified. At present, infrared stealth technology no longer focuses only on low infrared emissivity, but from multiple perspectives to achieve target stealth, such as the tunability of optical properties, good thermal management, and multi‐spectral compatibility stealth. At the same time, the infrared stealth of the target is gradually shifted from passive to active, emphasizing dynamic integration of the target and the environment. This review summarizes research progress, development, and application of infrared stealth materials. Camouflage dye and infrared stealth coating are classified as traditional technologies, however new developments and novel processes from literature can be constantly retrieved over the years. In addition to dyeing/coating technologies, this review also highlights advanced infrared stealth materials such as thermal insulation materials, phase change materials, electrochromic materials, metamaterials, and bionic materials. Outlines of the advanced technologies are mainly focused on those published in recent years. Challenges and prospects for the future development of infrared stealth materials are presented at the end of the review.

Performance of the Multilayer Film for Infrared Stealth based on VO2 Thermochromism

Performance of the Multilayer Film for Infrared Stealth based on VO2 Thermochromism

Lightweight Dual-Functional Segregated Nanocomposite Foams for Integrated Infrared Stealth and Absorption-Dominant Electromagnetic Interference Shielding

HighlightsLightweight dual-functional segregated nanocomposite foams are developed via the supercritical CO2 (SC-CO2) foaming combined with hydrogen bonding assembly and compression molding strategyThe segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity.Excellent absorption-dominant electromagnetic interference shielding performances are achieved owing to the synchronous construction of microcellular structures and segregated structures

A Study on Design and Microwave Characteristics of a RF/IR Multispectral Absorber

In this paper, a design for a radio frequency(RF) and infrared(IR) absorber with metasurfaces is discussed in microwave frequency bands. The RF absorber includes double layers of metasurfaces to operate in S- and X-bands. Effects of sheet resistance of the metasurfaces and thicknesses of dielectric supporting layers on reflection responses are investigated. An IR stealth layer incorporates an array of conductive grids with slits to reflect IR signals but to transmit RF signals and visible rays. Periodicity of the grids and slits is studied for transmission responses in the X-band and a surface area ratio. Reflection responses of the RF/IR multispectral absorber are found to be lower than -10 dB and -16 dB in the S- and X-bands, respectively, from full-wave simulation. Finally, the RF/IR multispectral absorber is fabricated and its reflection responses are measured to verify designed performance.

Electrochromic and thermal-control broadband stealth device based on AZO/Ag/AZO configuration electrodes

Existing stealth technologies have limitations including single bands and functions, and static and passive applications, so that targets cannot remain stealthy if multi-source detection approaches are used. With the wide application of visible-infrared (Vis-IR) detection and guidance technologies, there is an urgent need to develop advanced techniques for visible smart stealth and Vis-IR compatible stealth. In view of this, an electrochromic and thermal-control broadband stealth device based on AZO/Ag/AZO configuration electrodes was developed. The influencing mechanisms of microstructural characteristics of the conducting layer in the AZO/Ag/AZO configuration on the visible transmission spectra and infrared (IR) reflection spectra were revealed. Furthermore, a conducting layer enabling IR stealth with high visible transmittance was optimized, on which a V2O5 multi-color electrochromic film layer was prepared via self-assembled deposition. In this way, the device integrates multiple optical mechanisms including the visible-induced transmission, IR radiation suppression, and electrochromism to modulate optical properties in multiple bands. A technical route that integrates visible smart stealth and active suppression of IR radiation was established, which is conducive to improving the adaptive fusion ability under a multi-domain background and multi-band compatible optical stealth.

Sandwich-Structured Mxene/Waste Polyurethane Foam Composites For Highly Efficient Electromagnetic Interference, Infrared Shielding and Joule Heating.

Electromagnetic interference (EMI) shielding and infrared (IR) stealth materials have attracted increasing attention owing to the rapid development of modern communication and military surveillance technologies. However, to realize excellent EMI shielding and IR stealth performance simultaneously remains a great challenge. Herein, a facile strategy is demonstrated to prepare high-efficiency EMI shielding and IR stealth materials of sandwich-structured MXene-based thin foam composites (M-W-M) via filtration and hot-pressing. In this composite, the conductive Ti3C2Tx MXene/cellulose nanofiber (MXene/CNF) film serves as the outer layer, which reflects electromagnetic waves and reduces the IR emissivity. Meanwhile, the middle layer is composed of a porous waste polyurethane foam (WPUF), which not only improves thermal insulation capacity but also extends electromagnetic wave propagation paths. Owing to the unique sandwich structure of "film-foam-film", the M-W-M composite exhibits a high EMI shielding effectiveness of 83.37dB, and in the meantime extremely low emissivity (22.17%) in the wavelength range of 7-14µm and thermal conductivity (0.19W m-1 K-1), giving rise to impressive IR stealth performance at various surrounding temperatures. Remarkably, the M-W-M composite also shows excellent Joule heating properties, capable of maintaining the IR stealth function during Joule heating.

Electrostatic Encapsulation of Cobalt Ions into Crystalline Framework Derived Polymer Aerogel: Ultra-light, Pressure Resistant, Hydrophobic, Photothermal Conversion, Heat Insulation and Infrared Stealth

Electrostatic Encapsulation of Cobalt Ions into Crystalline Framework Derived Polymer Aerogel: Ultra-light, Pressure Resistant, Hydrophobic, Photothermal Conversion, Heat Insulation and Infrared Stealth

Multifunctional Ultrathin Metasurface with a Low Radar Cross Section and Variable Infrared Emissivity.

The development of stealth devices that are compatible with both infrared (IR) and radar systems remains a significant challenge, as the material properties required for effective IR and radar stealth are often contradictory. In this work, based on an IR electrochromic device (IR-ECD), concepts of metamaterial manipulating electromagnetic waves are applied to develop a multifunctional ultrathin metasurface with a low radar cross section (RCS) and variable infrared emissivity. This paper presents a linear-to-linear polarization conversion metasurface (PCM) designed by hollowing the IR-ECD. In this way, the IR-ECD based on polyaniline (PANI) can also modulate the reflection waves in the microwave band without affecting its features in the infrared region. Thus, the proposed metasurface integrates both microwave stealth and variable infrared emissivity through a single layer. The measured results show that a 10 dB RCS reduction is achieved in the band of 8.46-9.5 GHz, and the infrared emissivity can be adjusted from 0.870 to 0.513 in the infrared stealth band of 8-14 μm. Due to the ultrathin thickness (only 0.081λ0 at 9 GHz), low RCS in the X-band, and variable infrared emissivity, the designed multifunctional stealth metasurface has promising applications on military platforms with various surrounding environments.

Large-Scale, Mechanically Robust, Solvent-Resistant, and Antioxidant MXene-Based Composites for Reliable Long-Term Infrared Stealth.

MXene-based thermal camouflage materials have gained increasing attention due to their low emissivity, however, the poor anti-oxidation restricts their potential applications under complex environments. Various modification methods and strategies, e.g., the addition of antioxidant molecules and fillers have been developed to overcome this, but the realization of long-term, reliable thermal camouflage using MXene network (coating) with excellent comprehensive performance remains a great challenge. Here, a MXene-based hybrid network comodified with hyaluronic acid (HA) and hyperbranched polysiloxane (HSi) molecules is designed and fabricated. Notably, the presence of appreciated HA molecules restricts the oxidation of MXene sheets without altering infrared stealth performance, superior to other water-soluble polymers; while the HSi molecules can act as efficient cross-linking agents to generate strong interactions between MXene sheets and HA molecules. The optimized MXene/HA/HSi composites exhibit excellent mechanical flexibility (folded into crane structure), good water/solvent resistance, and long-term stable thermal camouflage capability (with low infrared emissivity of ≈0.29). The long-term thermal camouflage reliability (≈8 months) under various outdoor weathers and the scalable coating capability of the MXene-coated textile enable them to disguise the IR signal of various targets in complex environments, indicating the great promise of achieved material for thermal camouflage, IR stealth, and counter surveillance.

Molecular interface anchoring in PI-b-PDMS/SiO2@BN block copolymer foams for flexible, ultra-low dielectric, and enhanced terahertz communication performance

In the context of the future sixth-generation (6G) communication system, the development of multi-functional materials with ultra-low dielectric permittivity (Dk) and ultra-low dielectric loss (Df) is of paramount importance for the design of terahertz (THz) frequency electromagnetic wave transmission devices. In this work, polyimide-block-polydimethylsiloxane (PI-b-PDMS copolymer, PIC) material with low Dk, high flexibility and high supercritical fluid foaming ability was fabricated via copolymerization. Additionally, core–shell SiO2@BN nanofillers were synthesized by condensing tetraethyl orthosilicate (TEOS) on hexagonal boron nitride (BN) nanofiller surface. Subsequently, flexible polyimide/SiO2@BN foam was fabricated via supercritical N2 foaming. The resulting PIC/SiO2@BN nanocomposites exhibit exceptional flexibility and impressive thermal resistance (thermal decomposition temperature 472.2 °C). Notably, the incorporation of core–shell SiO2@BN nanofillers leads to the formation of a molecular interface anchoring structure through hydrogen bonding effect. This structure effectively reduced the mobility of the flexible PIC polymer chains on the SiO2@BN nanofiller surfaces. Consequently, the porous PIC/SiO2@BN materials show a low shrinkage ratio, low dielectric property (Dk = 1.21, Df = 0.012 at 1 THz), excellent THz transmission rate (91.4 %) and long distance 6G THz signal coverage (125.99 m). Furthermore, porous PIC/SiO2@BN materials show superior flame-retardant and thermal infrared stealth properties.

Revealing Surface/Interface Chemistry of the Ordered Aramid Nanofiber/MXene Structure for Infrared Thermal Camouflage and Electromagnetic Interference Shielding.

The past decade has witnessed the advances of infrared (IR) thermal camouflage materials, but challenges remain in breaking the trade-off nature between emissivity and mechanical properties. In response, we identify the key role of a moderate reprotonation rate in the aramid nanofiber (ANF)/MXene film toward a surface-to-bulk alignment. Theoretical simulation demonstrates that the ordered ANF/MXene surface eliminates the local high electric field by field confinement and localization, responsible for the low IR emissivity. By scrutinizing the surface/interface chemistry, the processing optimization is achieved to develop an ordered and densely stacked ANF/MXene film, which features a low emissivity of 16%, accounting for sound IR thermal camouflage performances including a wide camouflage temperature range of 50-200 °C, a large reduction in radiation temperature from 200.5 to 63.6 °C, and long-term stability. This design also enables good mechanical performance such as a tensile strength of 190.8 MPa, a toughness of 12.1 MJ m-3, and a modulus of 7.9 GPa, responsible for better thermal camouflage applications. The tailor-made ANF/MXene film further attains an electromagnetic interference (EMI) shielding effectiveness (40.4 dB) in the X-band, manifesting its promise for IR stealth compatible EMI shielding applications. This work will shed light on the dynamic topology reconstruction of camouflage materials for boosting thermal management technology.

Achieving the low emissivity of graphene oxide based film for micron-level electromagnetic waves stealth application

In recent years, the development of advanced materials with enhanced micron-level electromagnetic waves stealth properties has garnered significant attention due to their applications in fields such as military technology and thermal insulation. This study primarily investigates the stealth characteristics of materials within the 8–14 μm electromagnetic wave band, commonly known as the infrared (IR) spectrum. The effect of metallic Ag nanoparticles on the graphene oxide (GO) was obtained to achieve the excellent IR stealth ability. Specifically, Ag/GO composite films were prepared using a one-step reduction method and vacuum-assisted drying. The IR emissivity (8–14 μm) of the composites was significantly reduced with increasing Ag content, and the electrical conductivity of the materials was enhanced. When the Ag/GO mass ratio in the material was 1:2, the IR emissivity of the material at 8–14 μm was as low as 0.279, which was 62 % lower compared to GO. In addition, IR thermograms of the composites were analyzed using an IR thermographic camera. Obviously, the composites exhibited significant IR stealth properties when compared with those of GO. Thus, this work provides a reference for the preparation of carbon-based low IR emissivity materials for infrared stealth application.

Lightweight, Flexible, and Covalent-Bonding Phenolic Fabric Reinforced Phenolic Ablator for Thermal Insulation and Conformal Infrared Stealth.

Fiber-reinforced phenolic resin aerogel (FRPRA) composite materials are seductive candidates for high-temperature thermal protection owing to their low density, excellent thermostability, and thermal insulation. However, the intrinsic stiffness restricts their further application for high efficiency. We report a homogeneous and chemical bonding strategy for fabricating lightweight and flexible FRPRA with good ablative thermal insulation performance. The compressible (cyclic strain of 60%) and bendable (cyclic strain of 30%) abilities as well as the structural stability during ablation all benefit from the compatibility between the phenolic resin aerogel matrix and the phenolic fiber reinforcement. Additionally, low bulk density and thermal conductivity of 0.20 g cm-3 and 0.043 W m-1 K-1, respectively, endow the composite with efficient thermal insulation capability. With an 8 mm-thick coupon, the temperature of 200 °C can be decreased to 70.6 °C and the temperature around 1200 °C can be camouflaged to 78 °C through combining with the Al panel. The material also enables a conformal stealth of 600 °C based on its bendability. Hence, the composite has potential in applications of both static and dynamic thermal insulation.

Flexible Wearable Ti3C2Tx Composite Carbon Fabric Textile with Infrared Stealth and Electromagnetic Interference Shielding Effect

AbstractTi3C2Tx materials have been developed to have application space in many fields, but there are not many works that can be compatible with infrared (IR) stealth and electromagnetic interference (EMI) shielding at the same time. To realize the multiband high EMI shielding of Ti3C2Tx materials, and to achieve stealth effect in the IR band, in this work, a composite textile is prepared by combining the Ti3C2Tx material with a carbon cloth and sputtering a very thin gold film on the surface. This composite textile can realize high EMI shielding compatible with IR stealth, in which the EMI shielding efficiency for microwave Xa‐band (8GHza‐12.4GHz) is up to 71.8 dB, for microwave Kaa‐band (26.5GHza‐40GHz) is up to 75.02 dB, and for terahertza‐band is about 30 dB. IR emissivity is as low as 0.1, and the lowest emissivity under a certain temperature reaches 0.07, which can withstand a high temperature of 500 °C. In addition, this composite textile has flexible and bendable wear. The thickness of the whole textile is about 400 µm, of which the Ti3C2Tx material thickness is only about 10 µm, the thinnest reaches 2 µm. Such a textile can be used in both people's livelihood and military applications, which has far‐reaching significance.

Efficient Electromagnetic Wave Absorption and Thermal Infrared Stealth in PVTMS@MWCNT Nano-Aerogel via Abundant Nano-Sized Cavities and Attenuation Interfaces

HighlightsPVTMS@MWCNT nano-aerogel with nano-pore size and abundant heterogeneous interface was fabricated via radical polymerization, sol–gel transition and CO2 drying.The nano-aerogel shows superior electromagnetic wave absorption property (RLmin = −36.1 dB and cover all Ku-band) and thermal infrared stealth property (ΔT reached 60.7 °C).Layered nano-aerogel/graphene film with high EMI shielding and absorption properties was obtained;