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Title: Polygonization and Anomalous Graphene Interlayer Spacing of Multi-Walled Carbon Nanofibers

Abstract

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.

Authors:
 [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931489
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 75
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; CARBON FIBERS; NANOTUBES; LAYERS; ENTROPY; GRAPHITE; SHAPE

Citation Formats

Yoon, Mina, Howe, Jane Y, Eres, Gyula, and Zhang, Zhenyu. Polygonization and Anomalous Graphene Interlayer Spacing of Multi-Walled Carbon Nanofibers. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.165402.
Yoon, Mina, Howe, Jane Y, Eres, Gyula, & Zhang, Zhenyu. Polygonization and Anomalous Graphene Interlayer Spacing of Multi-Walled Carbon Nanofibers. United States. doi:10.1103/PhysRevB.75.165402.
Yoon, Mina, Howe, Jane Y, Eres, Gyula, and Zhang, Zhenyu. Mon . "Polygonization and Anomalous Graphene Interlayer Spacing of Multi-Walled Carbon Nanofibers". United States. doi:10.1103/PhysRevB.75.165402.
@article{osti_931489,
title = {Polygonization and Anomalous Graphene Interlayer Spacing of Multi-Walled Carbon Nanofibers},
author = {Yoon, Mina and Howe, Jane Y and Eres, Gyula and Zhang, Zhenyu},
abstractNote = {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.},
doi = {10.1103/PhysRevB.75.165402},
journal = {Physical Review B},
number = ,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}