- Description of the effort: This research seeks to develop the next generation of superstrong carbon nanofibers (CNF) by engineering their molecular structure. The carbon nanofibers are fabricated via thermal treatments of polymeric precursors, mainly electrospun polyacrylonitrile (PAN). We view CNFs as composite nanostructured materials, composed of turbostratic domains (defective graphitic nanoparticles, grown out of PAN) in an amorphous matrix. Our current efforts is focused on inducing the basal planes of turbostratic domains with the nanofiber axis to better exploit the strength of C-C sp2 bonds. This research includes material processing and characterization at the nanoscale, via innovative processing techniques and use of micromachined devices. In later stages of the project we will also focus on utilizing the novel CNFs in flywheels to enhance the storage energy density.
Figure: Top Left: SEM Cross section of a bundle of CNFs, Top Right: A single CNF failed in tension on a MEMS device, Bottom: Stress-strain curve of CNFs as a function of the hot-drawing ratio applied to their precursors
- Main findings so far:
- Hot drawing the precursor in CNFs can lead to significant improvement in strength and modulus by as much as 200%. This improvement in CNF properties is a result of the enhanced alignment of turbostratic domains with the fiber axis.
- The strength of CNFs do not seem to depend on surface defects as large as 10s of nm, which is the critical flaw size in CNFs.
- Funded by AFOSR & QNRF
- Senior personnel involved: Dr. M. Naraghi (Single PI – AFOSR), Drs. Palazzolo, Naraghi, Creasy and Tafreshi (PI is Dr. Palazzolo- QNRF)
- References
- 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).
- Naraghi M., Chawla, S., “Carbonized Micro- and Nanostructures: Can Downsizing Really Help?”, Materials, 7(5), 3820-3833, (2014)