Single wall carbon nanotube fibers extruded from super-acid suspensions: Preferred orientation, electrical, and thermal transport

Fibers of single wall carbon nanotubes extruded from super-acid suspensions exhibit preferred orientation along their axes. We characterize the alignment by x-ray fiber diagrams and polarized Raman scattering, using a model which allows for a completely unaligned fraction. This fraction ranges from 0.17 to 0.05+/-0.02 for three fibers extruded under different conditions, with corresponding Gaussian full widths at half maximum (FWHM) from 64degrees to 44degrees+/-2degrees. FWHM, aligned fraction, electrical, and thermal transport all improve with decreasing extrusion orifice diameter. Resistivity, thermoelectric power, and resonant-enhanced Raman scattering indicate that the neat fibers are strongly p doped; the lowest observed rho is 0.25 mOmega cm at 300 K. High temperature annealing increases rho by more than 1 order of magnitude and restores the Raman resonance associated with low-energy van Hove transitions, without affecting the nanotube alignment. (C) 2004 American Institute of Physics.