Jianle Xu

Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties.

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.

The synthesis and excellent electromagnetic radiation absorption properties of core/shell-structured Co/carbon nanotube–graphene nanocomposites

Through the reduction process involving Co3O4/reduced graphene oxide and acetylene, core/shell structured Co/carbon nanotube–graphene nanocomposites were synthesized on a large scale. Because of their special structure, high attenuation constant and good complementarity between magnetic loss material and dielectric loss material, the obtained Co/carbon nanotube–graphene nanocomposites exhibited very attractive microwave absorption. An optimal reflection loss (RL) of up to −65.6 dB at 12.4 GHz was observed with a thickness of 2.19 mm, and RL values below −20 dB were obtained in almost the entire frequency range. Therefore, a simple approach was proposed to explore the high-performance microwave-absorbing materials as well as expand the fields of application of graphene-based materials.

Synthesis of high purity chain-like carbon nanospheres in ultrahigh yield, and their microwave absorption properties

Over Fe/SnO2 nanoparticles generated by a combined sol–gel/reduction method, high purity chain-like carbon nanospheres (CNSs) could be synthesized in large quantities through the catalytic decomposition of acetylene at 700 °C. The effect of SnO2 content on the yield, microstructure and microwave absorbing properties of the obtained CNSs were studied in detail. The results demonstrate that the content of SnO2 has a great impact on the yield and dimensions of the obtained CNSs, and an ultrahigh yield of 309 was reported. Moreover, the smaller size of chain-like CNSs, which can be obtained over the catalysts with higher SnO2 content, exhibit enhanced microwave absorption properties due to their better complementarities between the dielectric and magnetic tangent loss. Based on the results, we also discuss the possible formation mechanism of CNSs. Therefore, we propose a simple and environmentally-friendly route for the mass production of chain-like CNSs with high purity, and the as-synthesized chain-like CNSs exhibit good microwave absorbing abilities.

Morphology-controllable synthesis of carbon nanomaterials directly on Al2O3 substrates, and their photoluminescence

By controlling the growth temperature, different categories of carbon nanomaterials (CNMs) such as carbon nanocoils (CNCs) and chain-like carbon nanospheres (CNSs) can be synthesized directly over Al2O3 substrate without using any transition-metal catalysts. It is proposed that the Al2O3 particles play a key role in the CNM growth, and the reaction temperature has a great impact on the morphology of the obtained CNMs. Furthermore, the photoluminescence studies indicate that the obtained CNCs and chain-like CNSs show different optical properties, which suggest that the optical properties of the obtained CNMs may be tuned by controlling their structures.