PI/BaF12O19/CS/MWCNTs coating with porous PI-walled encapsulation structure enables thickness-insensitive and robust microwave absorption

This work proposes a generalizable structural strategy for designing microwave-absorbing coatings that are both thickness-tolerant and disturbance-resistant. Here, we develop a coating based on a porous PI wall-encapsulated filler structure, in which the unique pore-wall interfaces markedly smooth the thickness evolution of impedance matching and attenuation, enabling effective Ku -band absorption over a 2.5–3.1 mm thickness window. An appropriate composition ratio combined with PI-encapsulated porous structure collectively achieves thickness-insensitive strong absorption performance. To evaluate its anti-interference capability, short-term surface oxidative etching tests were performed. The results show that, even after surface erosion, the internal wall-encapsulated network preserves stable Ku -band absorption and radar-cross-section reduction, maintaining the thickness-insensitive characteristics.