- Description of the effort: This effort seeks to drastically enhance the degree of graphitization and graphitic order in carbon nanofibers (CNFs) by benefiting from the graphitic nanoparticle inclusions (such as CNTs) in the precursors . This research includes innovative material processing and characterization at the nanoscale, and use of micromachined devices for nanoscale mechanical testing. The avenues for structural defect removal will be based on enhancing the crystalline order in PAN precursors and suppressing chain relaxation which would otherwise lead to alignment loss, and templated graphitization all to be achieved due to PAN-CNT interactions. At this stage, we are trying to exploit the removable functional groups on the surface of CNTs to enhance dispersion, while promoting the templating effect of CNTs.
Figure: Top: (A) Electrospinning experimental set-up and (B) obtained aligned PAN/CNTs nanofiber ribbons and (C) hot-drawing of nanofiber ribbon. Bottom: (A) Modulus reinforcement efficiency of CNTs for PAN/CNTs with λ=4 and schematic description of the effect of CNT dispersion on interphase area, in which black circles represent CNTs, gray regions represent bulk PAN nanofiber matrix, and orange regions represent highly ordered interphase regions. (B) TEM image of a protruded CNT with polymer sheath around it, pointing to the strong interactions between CNTs and the polymer. The region shown in a dotted box in the top figure is shown in higher magnification in the bottom image.
- Main findings so far:
- CNTs can nucleate PAN crystallization in electrospun nanofibers, leading to the formation of an extended chain structure, which can serve as the precursors for low-defect density turbostratic domains in CNFs.
- The addition of CNTs will also drastically influence the stabilization conditions of PAN, by suppressing chain relaxation.
- Funded by AFOSR
- Senior personnel involved: Dr. M. Naraghi (Single PI)
- Cai J., Chawla S., and Naraghi M., “Microstructural Evolution and Mechanics of Hot-drawn CNT-Reinforced Polymeric Nanofibers”, Carbon, in press (2016).
- Cai J. and Naraghi M., “Computational Analysis of Electrical Conduction in Hybrid Nanomaterials with Embedded Non-penetrating Conductive Particles”, Modelling Simul. Mater. Sci. Eng. 24, 065004 (15pp) (2016).