Mechanical properties of PAN-derived carbon nanofibers for polymer nanocomposites

To date nanofiber-based composites have been fabricated with randomly dispersed vapor grown carbon nanofibers (VGCNF)s and carbon nanotubes. Ordered carbon nanofibers as fabricated from electrospinning of polyacrylonitrile (PAN) pre-cursors are alternatives to randomly dispersed nanofibers. In this study, the mechanical properties of individual PAN-derived carbon nanofibers were measured as a function of carbonization temperature and nanofiber diameter. The carbonization temperature was varied between 800-1100 °C to quantify its effect on the fiber tensile strength. The resulting carbon nanofibers had smooth surfaces while remaining as aligned as the pre-cursor electrospun PAN nanofibers. The microscale tensile experiments on individual carbon nanofibers were conducted with the aid of microfabricated (MEMS) testing devices. The tested carbon nanofibers were tens of microns in length and 200-450 nm in diameter. Their failure strength increased with the carbonization temperature as it was expected for heat-treated carbon. The tensile strengths of nanofibers carbonized at 800°C and 1100°C followed Weibull distributions with Weibull moduli between 5 and 6, which indicates an average scatter of the defect sizes in the fibers.