Synthesis of yolk-shell structured carbonyl iron@void@nitrogen doped carbon for enhanced microwave absorption performance

Although carbonyl iron powders (CIP) have already been used as microwave absorbing material for human health, wireless communication safety and defense stealth technology, it is difficult to implement both thin coating thickness and broadband absorption capability. Herein, core-shell structured CIP@-SiO2@Nitrogen doped carbon (NC) microspheres were fabricated by a two-step process followed by a pyrolysis process and the yolk-shell structured CIP@void@NC microspheres were obtained by alkaline hydrothermal etching. The phase structure, micromorphology, magnetic properties, and electromagnetic parameters of yolk-shell structured CIP@void@NC microspheres were investigated by variously analytical techniques. The yolk-shell structured CIP@void@NC microspheres shown enhanced electromagnetic wave absorption properties both in effective absorption bandwidth (EAB, RL <= -10 dB) and absorption intensity compared with single CIP. The maximum reflection loss value is -25.7 dB at 17.2 GHz and the EAB can reach to 6.9 GHz (11.1-18 GHz) at a coating thickness of 1.7 mm for yolk-shell structured CIP@void@NC microspheres. The results indicated that the yolk-shell structured CIP@void@NC microspheres are expected to be a promising candidate as the high-performance microwave absorbing material. (C) 2019 Published by Elsevier B.V.