Structure and electrical transport properties of electrospun carbon nanofibers/carbon nanotubes 3D hierarchical nanocomposites: effect of the CCVD synthesis conditions.

The aims of this work were analysis of the effect of the synthesis conditions on the microstructure, structure, and electrical properties of electrospun carbon nanofibers/disordered carbon nanotubes (eCNF/dCNT) nanocomposites, and analysis of the correlations between these properties. The nanocomposites were obtained in the combined process involving electrospinning of precursor nanofibers and catalytic chemical vapor deposition (CCVD) synthesis of carbon nanotubes directly on the surface of nanofibers. The evaluation of microstructural-structural characteristics was conducted using microscopic, spectroscopic, and diffractometric methods. Electrical properties were investigated through measurements of temperature-dependent conductivity, and interpreted in terms of Mott's variable range hopping model. The study showed that the control of the temperature and duration of CCVD synthesis of CNT enables tailoring of the microstructure, defect density, and electrical transport in nanocomposites. Increasing the temperature up to 850 °C led to extension of the planar π-conjugated structure of nanoprotrusions, which resulted in facilitated conductivity of nanocomposites. The prolongation of the CCVD growth significantly increased the amount, and length of nanoprotrusions, which resulted in further enhancement of conductivity. The analysis of Raman spectra suggests the existence of an interesting correlation between the half-width of the G-band and T0 parameter describing the electrical properties. The study provides a solid background and route map for the synthesis of eCNF/CNT nanocomposites in applications such as energy storage and conversion, electrochemistry, nanoelectronics, semiconductors etc. [ABSTRACT FROM AUTHOR]