TY - JOUR
T1 - Structural characterization of exfoliated graphite nanofibers
AU - Lueking, Angela D.
AU - Gutierrez, Humberto R.
AU - Fonseca, Dania A.
AU - Dickey, Elizabeth
N1 - Funding Information:
Deepa Narayanan and Sabil Huda assisted in material preparation. Dirk Van Essandelft obtained the Raman data with direction from Jacob Caulkins. The work was funded by the Pennsylvania State University, including the Material Research Institute, the Energy Institute, and the Penn State Institutes for the Environment.
PY - 2007/4
Y1 - 2007/4
N2 - Structural characterization of exfoliated graphite nanofibers (EGNFs) with transmission electron microscopy (TEM) and high-angle annular dark-field-scanning TEM (HAADF-STEM) indicates exfoliation has led to structural expansion along the fiber axis, with discrete domains of graphitic nanocones separated by gaps ranging from 50 to 500 Å. Image contrast in HAADF-STEM demonstrates that structural expansion dominates over chemical etching. Raman spectroscopy indicates the EGNF is more graphitic than the precursor, and the disappearance of the characteristic defect (D) peak with multi-wavelength excitation is inconsistent with the presence of amorphous carbon. The highly expanded EGNF structure oxidizes at two distinct rates at 750 °C in CO2, leading to a highly-disordered graphitic fiber, with apparent collapse of the expanded structure as no gaps or discrete graphitic domains are observed after oxidation. Variation in the heat input per intercalant mass during thermal shock leads to changes in fiber morphology, including the extent of fiber expansion, the number of defects and pores observable within the fiber via TEM, and the surface area measured by nitrogen adsorption.
AB - Structural characterization of exfoliated graphite nanofibers (EGNFs) with transmission electron microscopy (TEM) and high-angle annular dark-field-scanning TEM (HAADF-STEM) indicates exfoliation has led to structural expansion along the fiber axis, with discrete domains of graphitic nanocones separated by gaps ranging from 50 to 500 Å. Image contrast in HAADF-STEM demonstrates that structural expansion dominates over chemical etching. Raman spectroscopy indicates the EGNF is more graphitic than the precursor, and the disappearance of the characteristic defect (D) peak with multi-wavelength excitation is inconsistent with the presence of amorphous carbon. The highly expanded EGNF structure oxidizes at two distinct rates at 750 °C in CO2, leading to a highly-disordered graphitic fiber, with apparent collapse of the expanded structure as no gaps or discrete graphitic domains are observed after oxidation. Variation in the heat input per intercalant mass during thermal shock leads to changes in fiber morphology, including the extent of fiber expansion, the number of defects and pores observable within the fiber via TEM, and the surface area measured by nitrogen adsorption.
UR - http://www.scopus.com/inward/record.url?scp=33846554216&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33846554216&partnerID=8YFLogxK
U2 - 10.1016/j.carbon.2006.11.023
DO - 10.1016/j.carbon.2006.11.023
M3 - Article
AN - SCOPUS:33846554216
SN - 0008-6223
VL - 45
SP - 751
EP - 759
JO - Carbon
JF - Carbon
IS - 4
ER -