Structure and purity of single walled carbon nanotube samples

Pulsed neutron diffraction has been used to characterize the microscopic structure and purity of single walled carbon nanotubes samples produced by arc discharge. We employed a time of flight diffractometer whose performance in measuring the microscopic structural properties of light-mass materials is well known and recognized. The extended Q-range of the instrument allows for a direct inversion of the data to determine the radial distribution function of the carbon atoms. This is compared with the corresponding function produced by computer simulation. In addition, the absolute calibration of the neutron diffraction data evidences anomalies in the diffraction spectra of the carbon nanotubes, especially at the level of the total scattering section, that could not be observed in previous neutron scattering experiments. These are attributed to the presence of a substantial amount of spurious carbonaceous material that was not quantitatively detected with more conventional diagnostic techniques.