Tailoring of a robust asymmetric aramid nanofibers/MXene aerogel film for enhanced infrared thermal camouflage and Joule heating performances

The development of infrared(IR)surveillance technology has led to a growing interest in thermal camouflage.However,the trade-off relationship between low IR-emissivity and thermal insulation hinders the advance of thermal camouflage materials.Herein,guided by multi-physics simulation,we show a design of asymmetric aramid nanofibers/MXene(ANF/MXene)aerogel film that realizes high-efficient thermal camouflage applications.The rationale is that the asymmetric structure contains a thermal-insulation three-dimensional(3D)network part to prevent effective heat transfer and a low IR-emissivity(~0.3)dense surface layer to suppress radiative heat emission.It is remarkable that the synergy mechanism in the topology structure contributes to over 40%reduction of target radiation temperature.Impressively,the tailored asymmetric ANF/MXene aerogel film also enables sound mechanical properties such as a Young’s modulus of 44.4 MPa and a tensile strength of 1.3 MPa,superior to most aerogel materials.It also exhibits great Joule heating performances including low driving voltage(4 V),fast thermal response(<10 s),and long-term stability,further enabling its versatile thermal camouflage applications.This work offers an innovative design concept to configure multifunctional structures for next-generation thermal management applications.

Scalable van der Waals graphene films for electro-optical regulation and thermal camouflage

Graphene exhibits enormous advantages in mid-infrared(MIR)regulation because of the active control,precise regulation,and large modulation depth.Such graphene films are prepared via chemical vapor deposition(CVD)or reduction,which cannot realize large-scale production and limit the applications.Graphene films with van der Waals(vdW)structure enable excellent mechanical and electrical performance for flexible electrodes and electronics and might be a candidate for MIR regulation.However,current techniques for preparing vdW graphene films require binder or solution assistance,resulting in chemical residues and performance degradation.Here,a new strategy for preparing large-area vdW graphene films by simple mechanical adhesion without any additives was proposed.By selecting the carriers and substrates with proper fracture energies,graphene nanosheets can be transferred from one polymer to another with a layer-by-layer structure.The obtained graphene films possess desired thickness and comparable electrical conductivity(92.8±4.6 ohm sq–1)with those by chemical vapor deposition.They are of high compactness even for ions to intercalate reversibly,which exhibit excellent electrochemical activity and electro-optical regulation capability,effectively suppressing 90%thermal radiation.This strategy can be extended to prepare high-performance vdW graphene films on various polymer substrates and used for sustainable and smart electro-optical applications.

Heat Transfer Characteristics of the Microfluidic Biomimetic Chameleon Skin with Active Thermal Camouflage

Natural organisms have different techniques to avoid enemies,such as chameleon skin with innate camouflage ability to change with the surrounding environment.Inspired by this,a microfluidic biomimetic chameleon skin based on infrared(IR)information processing is proposed for active thermal camouflage in a dynamic infrared background.Microfluidic circulation in microcavities distributed under the skin is controlled by a thermal camouflage system.The structure and working principle of the biomimetic skin are introduced,and the thermal camouflage system is established and tested to explore the heat transfer characteristics between the skin and the fluid.The mechanism of collecting the background infrared information and regulating the skin temperature through the control signal generated by the infrared information processing system is illustrated.Furthermore,the dynamic thermal response of the skin is tested when transitioning between different temperature backgrounds,modeling the ambient temperature of the sand,woodland and lakes where chameleons live.The performance of the skin is evaluated by measuring the camouflage responding time of the skin to an external heat source.The results show that the chameleon biomimetic skin is naturally transitioned and matched by infrared information processing and microfluidics.The limitation that the conventional thermal camouflage technology cannot adapt to the dynamic combat environment is overcome and the weaknesses of a small camouflage band range and a single form of camouflage are resolved in this study,thus effectively improving the target’s survivability in combat.

Multifunctional MXene/Carbon Nanotube Janus Film for Electromagnetic Shielding and Infrared Shielding/Detection in Harsh Environments

Multifunctional,flexible,and robust thin films capable of operating in demanding harsh temperature environments are crucial for various cutting-edge applications.This study presents a multifunctional Janus film integrating highly-crystalline Ti_(3)C_(2)T_(x) MXene and mechanically-robust carbon nanotube(CNT)film through strong hydrogen bonding.The hybrid film not only exhibits high electrical conductivity(4250 S cm^(-1)),but also demonstrates robust mechanical strength and durability in both extremely low and high temperature environments,showing exceptional resistance to thermal shock.This hybrid Janus film of 15μm thickness reveals remarkable multifunctionality,including efficient electromagnetic shielding effectiveness of 72 dB in X band frequency range,excellent infrared(IR)shielding capability with an average emissivity of 0.09(a minimal value of 0.02),superior thermal camouflage performance over a wide temperature range(−1 to 300°C)achieving a notable reduction in the radiated temperature by 243°C against a background temperature of 300°C,and outstanding IR detection capability characterized by a 44%increase in resistance when exposed to 250 W IR radiation.This multifunctional MXene/CNT Janus film offers a feasible solution for electromagnetic shielding and IR shielding/detection under challenging conditions.