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

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.