Rational Design of Skin Depth-Tuned Hollow Cobalt based Microtubes for High-Performance Microwave Absorption

The trend toward lightweight and highly integrated precision electronics has brought serious issues in electromagnetic (EM) compatibility, greatly boosting the use of microwave absorbing (MA) materials with high-efficiency microwave absorbance in low frequency, filling ratio, and thickness. This work sets out a method that modulates the wall thickness of one-dimensional (1D) hollow Co microtubes to skin depth, for achieving excellent MA performance in low frequency, filling ratio, and thickness, thereby clarifying this relationship between skin depth and absorption efficiency. Electroplating is employed to anchor Co particles and rGO onto carbon fibers, forming Co/rGO/CF composites. Subsequent thermal oxidation and reduction processes produce a one-dimensional hollow Co-based microtube (HCMT), which serves as the primary filler for microwave absorbance. Experimental and simulation results indicate that the 1D HCMT with controlled wall thickness exhibits great MA properties under extremely low filling ratios and thin sample thickness. Notably, when the wall thickness is optimized close to 0.33 μm, 1D HCMT-9 exhibits excellent MA performance with the broad effective absorption frequency (EAB) of 7.8 GHz at 3.0 mm thickness and the minimum reflection loss (RL_min) = −37.89 dB at 3.45 GHz at 1.0 mm thickness under 0.85 wt %. The study provides a feasible idea for the rational design and application of 1D nanotube structures for ultralight, thin, and high MA performance materials.