In order to explore high efficiency microwave absorption materials, heteronanostructured Co@carbon nanotubes-graphene (Co@CNTs-G) ternary hybrids were designed and produced through catalytic decomposition of acetylene at the designed temperature (400, 450, 500 and 550 °C) over Co3O4/reduced graphene oxide (Co3O4/RGO). By regulating the reaction temperatures, different CNT contents of Co@CNTs-G ternary hybrids could be synthesized. The investigations indicated that the as-prepared heteronanostructured Co@CNTs-G ternary hybrids exhibited excellent microwave absorption properties, and their electromagnetic and microwave absorption properties could be tuned by the CNT content. The minimum reflection loss (RL) value reached approximately −65.6, −58.1, −41.1 and −47.5 dB for the ternary hybrids synthesized at 400, 450, 500 and 550 °C, respectively. And RL values below −20 dB (99% of electromagnetic wave attenuation) could be obtained over the as-prepared Co@CNTs-G ternary hybrids in the large frequency range. Moreover, based on the obtained results, the possible enhanced microwave absorption mechanisms were discussed in details. Therefore, a simple approach was proposed to explore the high performance microwave absorbing materials as well as to expand the application field of graphene-based materials.

In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism.

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In this paper, α-Fe2O3 nanoparticles (NPs)-reduced graphene oxide (RGO), α-FeOOH nanorods (NRs)-RGO and porous α-Fe2O3 NRs-RGO could be selectively synthesized by hydrothermal method. The investigations indicated that the obtained α-Fe2O3 NPs, α-FeOOH NRs and porous α-Fe2O3 NRs were either attached on the surface of RGO sheets or coated uniformly by the RGO sheets. And the as-prepared nanohybrids exhibited excellent microwave absorption performance, which was proved to be ascribed to the quarter-wavelength matching model. The optimum reflection loss (RL) values for α-Fe2O3 NPs-RGO, α-FeOOH NRs-RGO and porous α-Fe2O3 NRs-RGO were ca. −32.3, −37.4 and −71.4 dB, respectively. Moreover, compared to the obtained α-Fe2O3 NPs-RGO and α-FeOOH NRs-RGO, the as-prepared porous α-Fe2O3 NRs-RGO nanohybrids exhibited enhanced microwave absorption properties because of their special structure and synergetic effect. The possible enhanced microwave absorption mechanisms were discussed in details. Our results confirmed that the geometrical morphology had a great influence on their microwave absorption properties, which provided a promising approach to exploit high performance microwave absorbing materials.