Reto Haggenmueller

Aligned single-wall carbon nanotubes in composites by melt processing methods

Abstract This Letter describes the production of single-wall carbon nanotube (SWNT) – polymer composites with enhanced mechanical and electrical properties and exceptional nanotube alignment. A combination of solvent casting and melt mixing was used to disperse SWNT materials in poly(methyl methacrylate) (PMMA). Composite films showed higher conductivity along the flow direction than perpendicular to it. Composite fibers were melt spun to achieve draw ratios between 20 and 3600. The elastic modulus and yield strength of SWNT–PMMA composite fibers increased with nanotube loading and draw ratio. Polarized resonant Raman spectroscopy indicates that the nanotubes in the fibers are well aligned, with mosaic distribution FWHMs as small as 4°.

Magnetically aligned single wall carbon nanotube films: preferred orientation and anisotropic transport properties

Thick films of single wall carbon nanotubes (SWNT) exhibiting in-plane preferred orientation have been produced by filter deposition from suspension in strong magnetic fields. We characterize the field-induced alignment with x-ray fiber diagrams and polarized Raman scattering, using a model which includes a completely unaligned fraction. We correlate the texture parameters with resistivity and thermal conductivity measured parallel and perpendicular to the alignment direction. Results obtained with 7 and 26 T fields are compared. We find no significant field dependence of the distribution width, while the aligned fraction is slightly greater at the higher field. Anisotropy in both transport properties is modest, with ratios in the range 5–9, consistent with the measured texture parameters assuming a simple model of rigid rod conductors. We suggest that further enhancements in anisotropic properties will require optimizing the filter deposition process rather than larger magnetic fields. We show that both ...

Electrical and Thermal Properties of C60‐filled Single Wall Carbon Nanotubes

We measured temperature‐dependent resistivity ρ, thermal conductivity κ and thermopower S of C60@SWNT (“peapods”). C60 filling reduces ρ much less than alkali metal doping at all T, indicating weak charge transfer. κ is enhanced by filling, the enhancement showing interesting structure vs. T for which we give a tentative explanation. S is reduced at all T by C60 filling, which we explain by a) C60@SWNT blocking some of the oxygen doping sites, and b) weak disorder on the 1‐D chain which reduces the mean free path of tube phonons and thus the phonon drag contribution.