Probing Mechanical Properties of Graphene with Raman Spectroscopy

The use of Raman scattering techniques to study the mechanical properties of graphene films is reviewed here. The determination of Gruneisen parameters of suspended graphene sheets under uni- and bi-axial strain is discussed and the values are compared to theoretical predictions. The effects of the graphene-substrate interaction on strain and to the temperature evolution of the graphene Raman spectra are discussed. Finally, the relation between mechanical and thermal properties is presented along with the characterization of thermal properties of graphene with Raman spectroscopy.Comment: To appear in the Journal of Materials Scienc

WTC2005-63550 FRICTIONAL AND ELECTRICAL PROPERTIES OF MULTIWALLED CARBON NANOTUBES

ABSTRACT This presentation examines the tribological properties and contact resistance of oriented capped carbon multiwalled nanotube (MWNT) films. Highly anisotropic tribological behavior of MWNT films oriented in mutually orthogonal directions is observed. The average values of coefficient of friction varied from high values (µ=0.795) for vertically aligned nanotubes grown on rigid substrates to low values (µ=0.090) for the same nanotubes dispersed flat on the same substrates. The results were insensitive to humidity, which is in contrast to graphite materials. The multiwalled nanotube layers also had a monotonic decrease in friction coefficient with increased surface temperature in both orientations, having a 32% drop in friction coefficient over a 73°C temperature rise. Preliminary results from contact resistance measurements of nanotube films grown through a porous alumina are investigated as a function of applied static load

Optical Spectra of Carbon Nanotubes for Stress Measurements of Advanced Aerospace Structures

The potential of carbon nanotubes being utilized for structural applications presents a need to develop non-invasive measurement capabilities for tailoring of reinforcements and to establish the structural integrity of such materials. This research is focused on developing relationships between mechanical properties and the optical spectra of single-walled carbon nanotubes. Laser excitation wavelengths were varied and effects on the G bands of the Raman spectra are presented here. Results of an in-situ thermal experiment on bulk carbon nanotube samples show the temperature dependency of these bands, which are commonly used to quantify the elastic modulus for CNT composites. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc