Polyacrylonitrile (PAN) based electrospun carbon nanofibers (ECNFs): Probing the synergistic effects of creep assisted stabilization and CNTs addition on graphitization and low dimensional electrical transport

We report on the fabrication of Polyacrylonitrile (PAN) based electrospun carbon nanofiber (ECNF) reinforced with multi-walled carbon nanotubes (MWCNTs) and characterization of the graphitic structure as well as electrical transport properties for four different ECNF systems. The different systems were obtained by the combination of two different ways of cyclization for pristine PAN and PAN with CNTs addition (PAN/CNT), typically by the application of constant creep stress and a constraint fixing. The addition of CNTs improved the graphitic structure of PAN. For the detailed analysis of different systems, carbonization was performed at 1700 °C and the graphitic structures were characterized. The CNTs improve the alignment of graphitic domains even for non-creep cyclized systems. The application of creep stress during cyclization results in highly aligned graphene planes. However, the creep stress cyclized PAN/CNT system exhibited a reduction in the alignment of graphene planes coming along with the observation of discontinuous, randomly orientated domains and a reduced conductivity. The electrical anisotropy increased for creep cyclized PAN and PAN/CNT compared to non-creep stress cyclized system. Our findings reveal that electrical transport in carbon nanofibers need to be considered as a cumulative effect of hopping and band transport along chemically and structurally inhomogeneous ECNFs.