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

Lightweight infrared stealth and absorption-dominant electromagnetic interference(EMI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable electronics.Herein,lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO_(2)(SC-CO_(2))foaming combined with hydrogen bonding assembly and compression molding strategy.The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity,and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures.Particularly,the segregated nanocomposite foams present a large radiation temperature reduction of 70.2℃ at the object temperature of 100℃,and a significantly improved EM wave absorptivity/reflectivity(A/R)ratio of 2.15 at an ultralow Ti_(3)C_(2)T_(x) content of 1.7 vol%.Moreover,the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles.The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace,weapons,military and wearable electronics.

Electroless plating of copper layer on surfaces of urea-formaldehyde microcapsule particles containing paraffin for low infrared emissivity

A copper coating was deposited by electroless plating on the surfaces of urea-formaldehyde microcap- sules containing paraffin （UFP） particles. This composite microcapsule structure had low infrared OR） emissivity and maintained a constant temperature, and could be used in IR stealth applications. The eiectroless copper layer formation and its micro-appearance, and the effect of the copper layer on the IR emissivity and thermal properties of the composite microcapsules were investigated. The IR emissivity of the composite microcapsules at wavelengths of 1-14 μm gradually decreased with increasing copper mass on the surface. After formation of an integrated copper layer, the rate of IR emissivity decrease was lower. This is because the copper coating improves the surface conductivity of the UFP; a high conductivity results in high reflectivity, which leads to a decrease in IR emissivity. The lowest IR emissivity achieved was 0.68. The phase-change enthalpy of the composite microcapsules decreased with increasing amount of copper coated on the surface because of the high density of copper. When the mass increase of the UFP after electroless copper plating was about 300%, the composite microcapsules had low IR emissivity （about 0.8） and a high phase-change enthalpy （80J/g）.

Preparation and Characterization of Sn-doped ZnO Particles with Low Infrared Emissivity

Sn-doped ZnO particles were successfully synthesized by chemical co-precipitation method.Their morphology,phase,microstructure and infrared emissivity were characterized.The results show that the Sn-doped ZnO particles are of ellipsoid shape,their crystalline structure changed with thermal process temperature,the optimal thermal process temperature and Sn-doped proportion are 1000℃ and 15%,respectively,the minimum emissivity values are 0.42,0.28,0.46 and 0.48 corresponding to the infrared wavelengths of 0~∞,3~5,8~14 and 14~20 μm,which indicates that the Sn-doped ZnO particles have the application potential as low infrared emissivity material.

Visible transparent,infrared stealthy polymeric films with nanocoating of ITO@MXene enable efficient passive radiative heating and solar/electric thermal conversion

Visible transparent yet low infrared-emissivity(ε)polymeric materials are highly anticipated in many applications,whereas the fabrication of which remains a formidable challenge.Herein,visible transparent,flexible,and low-εpolymeric films were fabricated by nanocoating decoration of indium tin oxide(ITO)and MXene on polyethylene terephthalate(PET)film surface through magnetron sputtering and spray coating,respectively.The obtained PET-ITO@MXene(PET-IM)film exhibits lowεof 24.7%and high visible transmittance exceeding 50%,endowing it with excellent visible transparent infrared stealthy by reducing human skin radiation temperature from 32 to 20.8°C,and remarkable zero-energy passive radiative heating capability(5.7°C).Meanwhile,the transparent low-εPET-IM film has high solar absorptivity and electrical conductivity,enabling superior solar/electric to thermal conversion performance.Notably,the three heating modes of passive radiative and active solar/electric can be integrated together to cope with complex heating scenarios.These visible transparent low-εpolymeric films are highly promising in infrared stealth,building daylighting and thermal management,and personal precision heating.

Optical transparent metamaterial structure for microwave-infrared-compatible camouflage based on indium tin oxide

A visible transparent metamaterial absorber was designed and fabricated with ultrabroadband microwave absorption and low infrared emissivity to meet the increasing demand for multispectral compatible camouflage. The absorber was fabricated with a low-infrared emissive layer at the top, a microwave-absorbing layer in the middle, and a reflective layer at the bottom, which were separated by polymethyl methacrylate plates. The absorber showed an average visible transmittance of 55%, infrared emissivity of ~0.37, and effective microwave absorption bandwidth of 32.1 GHz with a total thickness of 3.0 mm. Furthermore,microwave absorption exhibited wide-angle stability and polarization insensitivity characteristics. The mechanism of microwave attenuation was further explored through effective electromagnetic parameters as well as surface current, electric field, magnetic field, and energy loss density distributions. The experimental results were consistent with those of the simulations and calculations, indicating the potential of the designed metamaterial absorber for future applications in multispectral compatible camouflage.