Structure-dependent electromagnetic wave absorbing properties of bowl-like and honeycomb TiO2/CNT composites

Materials that can efficiently absorb electromagnetic waves (EMWs) are required to deal with electromagnetic pollution. Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials, particularly when adjustment of the constitution or mixing ratio is limited. In this study, bowl-like and honeycomb titanium dioxide/carbon nanotube (TiO2/CNT) composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration, respectively. Compared to the honeycomb structure, the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization, and augmented multiple reflections. The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics. The bowl-like TiO2/CNT composite exhibited a minimum reflection loss (RLmin) of −38.6 dB (1.5 mm) with a wide effective absorption band (EAB; <−10 dB) of 4.2 GHz, while the honeycomb TiO2/CNT composite showed an RLmin of −34.8 dB (2.1 mm) with an EAB of 4.3 GHz. The required mixing ratio in the matrix was only 15 wt%, outperforming that of the most closely related composites. Thus, both the bowl-like and honeycomb TiO2/CNT composites are ideal candidates for light-weight and highly efficient EMW-absorbing materials.