Facile design and permittivity control of reduced graphene oxide foam/TiO2 3D composite towards lightweight and high-efficient microwave absorption

•Novel three dimensional TiO2/RGO composite were designed and synthesized.•Tunable dielectric loss was theoretically calculated and experimentally realized.•Competitive absorption performance was obtained by effective dielectric regulations.•Correlations between structure and property were deeply investigated and discussed. Tuning the electromagnetic parameters is a significant principle of developing high-performance microwave absorbers. However, controllably regulating the magnetic and dielectric properties of an electromagnetic composite is difficult because of the coordinated changes in both dielectric and magnetic properties. To deal with the issue, here we reported a three dimensional reduced graphene oxide (RGO) foam modified with dielectric TiO2 microrods through a facile hydrothermal process. Theoretical calculations were conducted based on transmission line and quarter wavelength theories to indicate the desired values of the complex permittivity for high absorbing properties, and precisely controlled dielectric variates of the composite samples were realized without the magnetic interferences. Benefiting from the structure and composition modulation, the composites exhibit a great improvement in both the impedance matching conditions and the microwave absorption properties. Consequently, the minimum reflection loss of −64.4 dB and broadened bandwidth of 5.4 GHz (12.5–17.9 GHz) were obtained. The method in this work provides a promising strategy of designing and fabricating high-performance dielectric microwave absorbers.