Fractal characterization for conductivity mechanism of single-walled carbon nanotube doped composites

The investigation of physical properties such as the electrical conductivity of vinyl ester/carbon nanotube/polymer systems with different ratios of carbon nanotubes has been a remarkable phenomenon recently. For this purpose, both neat materials without carbon nanotubes and single-walled carbon nanotube (SWCNT)-loaded vinyl ester resin-based composite materials were manufactured. To establish a relationship between the surface properties of the material and the conductivity mechanism in the material, the surface microstructure and conductivity behaviors of the materials are described comparatively using the fractal analysis method and impedance spectroscopy techniques. The surface topography of the samples was determined from microphotographs obtained by scanning electron microscopy (SEM). The SEM images showed that independent and different-sized clusters aggregated on the surfaces and internal structures of the materials. Surface coverage ratios and fractal dimension values were calculated by applying the fractal characterization method to the specimens. Surface coverage ratios and fractal dimensions in SWCNT-loaded nanocomposites were analyzed considering effects such as component dispersion and particle density compared to pure polymer. It was found that the fractal behavior of the nanotube-filled composite was one of the effective components in the formation of the conductive mechanism. Nyquist diagrams of materials obtained using the impedance results also confirmed the fractal analysis data. It was noticed from the curvature degree of the Nyquist plots that as SWCNT was added to the vinyl ester matrix, the efficiency of the interchain network of the nanotube-loaded material was significantly increased.