Modeling of Tunneling Distance Among Nearby Carbon Nanofibers to Control the Tunneling Resistance and Electrical Conductivity of Composites

A larger tunnel in polymer carbon nanofiber (CNF) composites (PCNFs) constrains the electron transport within nanocomposites, as these tunnels comprise adjacent nanoparticles separated by an insulating polymer film. However, the tunneling distance (λ) remains an unidentified parameter, which has not been thoroughly explored in previous studies. In this paper, we develop the Weber–Kamal and Deng–Zheng models for PCNF conductivity and assess their predictive accuracy using experimental data. The progressed expressions are then related to state the λ as a function of CNF concentration, percolation threshold, CNF size, interphase depth, CNF waviness, contact number, network fraction, and contact diameter. The effect of each parameter on λ is examined to validate the proposed equation. A lower percolation threshold, greater interphase depth, reduced waviness, higher contact number, larger contact diameter, and increased network fraction result in narrower tunnels. The maximum λ of 40 nm is noticed at the CNF radius (R) of 90 nm with a CNF length of 50 μm; nevertheless, R < 57 nm reduces λ to 1 nm. Consequently, the thickest and shortest CNFs yield the largest tunnels, while the narrowest tunnels are produced by the thinnest CNFs. These data emphasize the momentous impact of CNF size on the tunneling size manipulating the nanocomposite conductivity.