Integration of efficient microwave absorption and shielding in a multistage composite foam with progressive conductivity modular design†

Abstract

Ultra-efficient electromagnetic interference (EMI) shielding composites with excellent microwave absorbing properties are the most desirable solution for eliminating microwave pollution. However, integrating absorbing and electromagnetic shielding materials is a difficult challenge because they have different design strategies. In this work, the compatibility of high absorption and shielding capability based on progressive conductivity modular design was realized. Reduced graphene oxide@ferroferric oxide/carbon nanotube/tetraneedle-like ZnO whisker@silver/waterborne polyurethane (rGO@Fe₃O₄/CNT/T-ZnO@Ag/WPU) multistage composite foams with aligned porous structures were fabricated, which exhibited an excellent average EMI SE > 92.3 dB and remarkable microwave absorption performance with reflection loss < ?10 dB in the frequency range of 8.2–18.0 GHz. The average shielding effectiveness of reflection (SE_R) and reflectivity (R) are as low as 0.065 dB and 0.015, respectively. Besides, the correlations between the morphology and structure of the composite foam and the electromagnetic wave attenuation mechanism were established via electromagnetic simulation. Significantly, the integration of efficient absorbing and shielding materials was realized for the first time. Such composite foams with electromagnetic wave absorption and shielding characteristics are light weight and structurally designable with an adjustable shielding mechanism, and exhibit low filler consumption and high performance. They display promising applications in demanding electromagnetic environments. Our work provides a new strategy to design ultra-efficient EMI shielding materials with reliable absorption-dominated features.