Bio-based, phase-change MXene/CNT foams for integrated electromagnetic interference shielding, thermal management and infrared stealth

Abstract

The surge in wireless technologies and electronic devices has intensified the demand for next-generation materials with integrated electromagnetic interference (EMI) shielding. Yet, it remains a major challenge to integrate thermal insulation, thermal management and infrared stealth into a single system. Herein, bio-based Eucommia ulmoides gum (EUG) – a natural trans-1,4-polyisoprene rubber with high crystallinity and elasticity – was used to develop porous foams via a salt-sacrificial template method, guided by synergy strategy combining multiple working mechanisms. The synergistic conductive fillers, i.e. multi-walled carbon nanotubes (CNTs) and MXene, were concentrated within the EUG skeleton and on the surface. This arrangement facilitates the formation of an efficient conductive network, thereby enhancing the reflection of microwaves and infrared radiation. Additionally, the multi-level pores lead to multiple reflections and absorptions of EMI, while also impeding the heat conduction process. Meanwhile, EUG with phase change capability further regulates the surface temperature via heat absorption. Ultimately, EUG/CNT/MXene (ECM) foam with a thickness of 2 mm exhibited a shielding effectiveness (SE) of 49.7 dB in the X-band, a thermal conductivity of 0.15 W·m⁻¹·K⁻¹, a latent heat of 36.8 J·g⁻¹ and a temperature difference of 30.25 °C between opposite surfaces. Compared with EUG foam, ECM foam achieved a 28 % lower infrared emissivity and an 825 % higher compression strength. The temperature difference between the handheld foam and the environment was only 2.8 °C, indicating superior infrared stealth. Furthermore, the ECM foam demonstrated excellent phase change stability during thermal cycling. In the durability test, the SE value of ECM retained 83.5 % of its initial SE. This work provides a novel strategy for designing multifunctional EMI shielding materials.