Lightweight polyimide-derived carbon foams with anisotropic porous structures prepared by microwave-assisted foaming and carbonization for thermal insulation and EMI shielding applications

Abstract

Lightweight and anisotropic porous carbon materials have promising applications in thermal insulation and electromagnetic interference (EMI) shielding fields. Herein, lightweight polyimide foams (PIFs) with anisotropic pore structures were prepared by adopting a microwave-assisted foaming method and the obtained PIFs were employed as derivatives to fabricate carbon foams, i.e., PICFs. The PICFs with aligned ellipsoidal strip-like pore structures presented low volumetric shrinkage (44.87–50.24%) and weight loss (36.33–48.17%), along with favorable compressive strength (102.96 kPa), and high temperature thermal resistance. In addition, the anisotropic pore structure imparted efficient thermal insulation and infrared thermal stealth properties to PICFs, with thermal conductivity as low as 0.0356 W (m K)⁻¹ along the horizontal direction (perpendicular to the pore growth direction). When carbonized at 1400 °C, PICF₁₄₀₀ with a low density (22.9 kg m⁻³) and thin thickness (1.9 mm) exhibited a high electrical conductivity of 23.91 S m⁻¹ in the horizontal direction. The EMI shielding effectiveness (SE) and specific EMI SE reached as high as 53.2 dB and 12216 dB (g cm⁻²), respectively. Moreover, PICF₈₀₀ exhibited a high absorption coefficient of 0.91. Therefore, a facile strategy was proposed for fabricating lightweight PICFs which possess multifunctional properties enabling potential applications in high-end engineering sectors.