Highly oriented MXene/polyvinyl alcohol films prepared by scalable layer-by-layer blade coating for efficient electromagnetic interference shielding and infrared stealth

Controlling the orientation of two-dimensional MXene within layered films is essential to optimize or tune their mechanical properties and electromagnetic interference shielding (EMI) performance, but achieving the high orientation MXene layers on an industrial scale remains a challenging goal. In this paper, a scalable layer-by-layer blade coating (LbLBC) method was employed to fabricate highly oriented MXene/polyvinyl alcohol (PVA) films. During the LbLBC process, MXene/PVA colloid suffered a strong shearing effect, which induced the ordered alignment of MXene nanosheets along the direction of the blade movement. The orientation of MXene can be effectively adjusted by changing the scraping gap of LbLBC, achieving a maximum Herman orientation factor f of 0.81. As a result, the mechanical properties and EMI performance of the as-prepared MXene/PVA films are in direct proportion to their orientation, with the optimal values of tensile strength of 145.5 MPa, fracture strain of 19.6%, toughness of 17.7 MJ·m−3, and EMI shielding effectiveness of 36.7 dB. Furthermore, the inherently low mid-infrared (mid-IR) emissivity of MXene, combined with the densely oriented structure affords the composite films with IR stealth, resulting in a substantial decrease from 150 to 66.1 °C in the radiative temperature of a surface. Conclusively, these scalable MXene/PVA films exhibit remarkable potential for integration into the next generation of multifunctional protective camouflage materials.