Facile fabrication of sepiolite functionalized composites with tunable dielectric properties and their superior microwave absorption performance.

Although various materials have been studied for the purpose of microwave absorption (MA), natural sepiolite (SEP) has never been reported as MA absorber. Herein, the series of sepiolite@polyaniline composites (SEP@PANI-x) with "skeleton/skin" structure were fabricated through a facile in-situ polymerization technique and firstly developed as MA materials. The electrical conductivity and dielectric properties can be well controlled via modulating the PANI content in the composites. With a lower mass ratio of 30 wt%, it is worth noting that the optimized SEP@PANI-50 could simultaneously display the optimal minimum reflection loss (RL) of -50.23 dB and effective absorption bandwidth (EAB, RL < -10 dB) of 5.01 GHz with thicknesses of 2.5 and 1.8 mm, respectively. Moreover, when changing absorber thickness (1.5-5.0 mm), the RL values lower than -20 dB (99% absorption) are all achieved and the EAB ranges the entire Ku, X, and C bands. Such excellent MA performance comes from rich conductive network and polarization relaxation, which ultimately balance the impedance matching and attenuation ability. In view of its facile synthesis route, low-cost, lightweight and excellent MA performance, SEP@PANI-50 would be a very promising MA candidate in many practical applications. More importantly, we also think that our findings will expand the application of SEP-based composites in the electromagnetic field.