Characterization of carbon nanotube turfs by SEM analysis

Hina Malik

The numerous attractive electrical and mechanical properties of carbon nanotubes have drawn the focus of several research groups to this relatively new breed of technological materials. Vertically aligned carbon nanotube (VACNT) turfs are the intertwined structures and complex grass like assemblies of multi walled carbon nsanotubes grown vertically. There is a challenging lack of information required to fully understand the mechanism that involves and controls the turfs' structure and associated properties. For several applications in the regime of micro and nano electro-mechanical systems it is crucial to understand the combined behavior of CNT turfs rather than only the properties of a single carbon nanotube as it is well established fact that multi walled turf structures yield properties different to those shown by single walled carbon nanotubes. The purpose of this study was to investigate and characterize the mechanical properties of the vertically aligned carbon nanotube turfs (VACNTs). Four parameters namely diameter, density, tortuosity (straightness and entanglement) and path connectedness have been quantified in this current study. Of these parameters, last three have been alleged as the most valuable physical characteristics and can be responsible for any change in mechanical behavior of turfs. This study describes the stereology-assisted methodologies coupled with statistical data collection. Commercially available softwares like 'Image J', and 'KaleidaGraph' have been employed for analysis of scanning electron micrographs and to obtain various information about obtained data sets. Diameter, density, tortuosity and path connectedness were measured directly from high resolution scanning electron micrographs of CNT turfs and the results were compared against the mechanical behavior of these turfs obtained by nanoindentor. In the analyzed turfs, density seems somewhat inversely proportional to the reduced elastic modulus Er . The measured sum of angles (SOA) and path connectedness reveal the degree of entanglement or unalignment in the local regions of the turfs. In order to formulate a 'governing' equation that can control the relationship among various parameters, 3D information and further statistical data are required. The present study, however supplies the fundamental but decent and reliable bases to quantify vertically aligned carbon nanotube turfs (VACNTs) any further regarding their mechanical properties.

Characterization of carbon nanotube turfs by SEM analysis

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