Degree of conduction transfer through incomplete interphases controlling the conductivity of carbon nanofiber...

Assuming an incomplete interphase in carbon nanofiber (CNF)/polymer composites (PCNFs), the conduction transfer amount from the CNF to the polymer media, denoted as Y, is determined by the CNF length and the minimum length required for effective conduction transfer to the matrix (L_c). The real inverse aspect ratio, actual CNF volume fraction, percolation threshold, and the amount of network are all influenced by Y. Additionally, the Kovacs model is extended for PCNF conductivity to incorporate network concentration, real inverse aspect ratio, and tunneling resistance. The effects of parameters on the Y, percolation threshold, and composite conductivity are illustrated and analyzed. The calculated conductivity is compared with the measured conductivity of multiple samples to validate the proposed model. Shorter L_c, longer and thinner CNFs, and higher interphase conductivity lead to increased values of Y. Furthermore, a higher Y results in an inferior percolation and a greater network portion. For instance, when Y = 1, the percolation threshold reaches a maximum of 0.009, whereas for Y > 15, the percolation threshold decreases to 0.006, and the network fraction increases to 0.155 at Y = 21. Moreover, maximum values of Y = 20 and a 4 vol.% CNF can enhance the nanocomposite conductivity to 0.13 S/m, highlighting the direct influence of Y on the PCNF conductivity.