Directionally pressurized filtrated nitrogen-doped CNTs/RGO/carbon hollow sphere/CoNi sandwich buckypaper with superflexible, high-strength mechanical, and excellent microwave-absorbing properties

It remains a challenge to fabricate self-supporting superflexible high-strength films of multi-layered nanocomposites in one step using a simple method. Here, a unique sandwich multi-layer structured, superflexible, and high-strength buckypaper was one-step formed via Directional Pressure Filtration. The buckypaper used carbon nanotube (CNTs)-carbon hollow sphere/CoNi nanochains as the skin layer and reduced graphene oxide (RGO)-carbon hollow sphere/CoNi as the core layer. By constructing a transition layer between the core and skin layers, a natural changeover between layers was achieved, and the interlayer bonding was strengthened. The sandwich buckypaper had both high strength and superflexibility, with a maximum tensile strength of 21.6 MPa and a maximum tensile strain of 11.5 %. It was folded randomly along sharp creases (such as folded into an origami crane) without damage. With a minimum reflection loss of –66.03 dB and an effective absorption bandwidth of 5.0 GHz, it demonstrated excellent microwave-absorption property. The two-dimensional simulated RCS curves, covering angles from –60° to 60°, showed that within the skin-to-core mass ratio of 2:1 to 1:2, all RCS values stayed beneath –10 dB m²; at the mass ratio of 1:1, no scattering signal was observed. Its excellent microwave absorption performance and high-strength, superflexible mechanical properties endow it unique charm and potential application advantages in the field of wearable electronics.