Preparation of core-shell C@TiO2 composite microspheres with wrinkled morphology and its microwave absorption.

Abstract In this work, we successfully synthesize the core-shell structure carbon@titanium dioxide (C@TiO2) composite microspheres with wrinkled surface through a three-step method and build up the relationship between the TiO2 layer thickness and the microwave absorption property. The absorbing mechanism of the novel microsphere is revealed. Interface polymerization is applied for preparation of wrinkled poly glycidyl methacrylate/divinylbenzene polymer microspheres (PGMA/PDVB); Then, TiO2 layer is controllably coated on the surface of PGMA/PDVB microspheres by hydrolysis of tetrabutyl titanate (TBT); C@TiO2 composite microspheres are obtained by vacuum carbonization with PGMA/PDVB@TiO2 microspheres as the precursor. TiO2 layer thickness on the surface of C@TiO2 composite microspheres can be effectively adjusted by controlling the amount of TBT. When the amount of TBT is 0.75 mL, C@TiO2 composite microspheres exhibit the outstanding electromagnetic loss performance. The maximum reflection loss value (RLmax) reaches -49.21 dB at the thickness of 2 mm, corresponding effective absorption bandwidth is 5.27 GHz. The maximum effective absorption bandwidth is 5.5 GHz at 2.2 mm. The results show that the introduction of TiO2 can regulate electromagnetic parameters and enhance interface polarization ability. Meanwhile, the surface wrinkle structure offers more opportunities for multiple reflections of electromagnetic and introduces a large number of defective skeleton structure. The synergy of multiple advantages makes the absorbing performance of C@TiO2 composite microspheres significantly improved. This work plays a guiding role for the composition and the structure optimization of existing microwave absorbers.