Polygonization and Anomalous Graphene Interlayer Spacing of Multi-Walled Carbon Nanofibers
- ORNL
The graphene interlayer spacing in pure graphite is known to have a minimum value of dmin = 0.3354 nm, while defective graphites typically have larger interlayer spacings. Using transmission electron microscopy and X-ray diffraction, we find that the graphene interlayer spacing in multi-walled carbon nanofibers heat treated above ≈ 2800 K is distinctly smaller than dmin. To explain this unusual observation, we investigate the structural properties of carbon nanotubes using a multiscale approach rooted in extensive first-principles calculations, specifically allowing the nanotube cross-sections to polygonize. We show that, whereas normal nanotubes are favored energetically at low temperatures, the configuration entropy associated with Stone-Wales defect creation at high temperatures makes the polygonal shape of large nanotubes or nanofibers thermodynamically stable, accompanied by a reduction in the graphene interlayer spacing. These unique predictions are confirmed in further experimental tests.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 931489
- Journal Information:
- Physical Review B, Vol. 75
- Country of Publication:
- United States
- Language:
- English
Similar Records
High Capacity Adsorption—Dominated Potassium and Sodium Ion Storage in Activated Crumpled Graphene
Structural transformations of graphene exposed to nitrogen plasma: quantum chemical molecular dynamics simulations