(2lo) Boost up the Electrical Property of CNT Fibers By Governing Impurities on the Surface of CNT with Microwave-Assisted Purification

Carbon nanotube fibers (CNTFs) are attracting significant interest from various research fields due to their remarkable properties, such as high electrical conductivity, strength, flexibility, and light weight. The properties of CNTFs are profoundly influenced by the characteristics of carbon nanotubes (CNTs) used, such as impurities, surface state, and length. Therefore, a CNT purification process is inevitably to obtain high-performance CNTFs. In particular, the key to purification is to obtain impurity-free CNT by removing all extraneous materials.

Herein, we present an efficient two-step purification process to produce ultra-high-purity CNTs. Firstly, a microwave purification method rapidly eliminates the iron catalyst as well as the amorphous carbon species from the surface of CNTs. In the following step, subsequent thermal annealing treatment further reduces the residual amorphous carbon. Consequently, the iron catalyst content is reduced to less than 1 wt%, and amorphous carbon is removed, resulting in spotless ultra-high-purity CNTs. CNTFs prepared from the two-step purified CNTs exhibit significantly improved electrical conductivity properties compared to CNTFs derived from pristine and microwave-purified CNTs. The comparison of these CNTFs also confirms the influence of the amount and surface condition of amorphous carbon on the CNT surface on the electrical conductivity and mechanical strength of the fibers.