ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Characterization of Thermal Transport in Carbon Nanotube Yarns
Abstract
The macroscopic carbon nanotube (CNT) assembly has great potentials for thermal and electronic
applications due to the outstanding mechanical and physical properties of CNT. In this work, we directly
spin long CNT yarns (CNTYs), which consist of well-aligned and inter-connected CNTs, from an aerogel
form in a chemical vapor deposition reactor. To investigate the relationship between the thermal properties
and the micro- and nano-structures of CNTY, the as-spun CNTYs are subjected to different post-processes,
such as nitric acid treatment, twisting, and doping with Iodine. The defect concentrations are detected by
Raman spectroscopy, and the effective thermal conductivity is measured by a T-type probe. The acid
treatment tends to remove the impurity, induce defects and also decrease diameter. I-doped CNTY has two
new bands not associated with CNTs, and the ratio of the integrated intensities of D band and G band
increases from that of the as-spun yarns due to the formation of extra defect. It is found that, the lattice
thermal conductance per unit length decreases smoothly with increasing defects induced by acid treatment
and I-doping. The twisted yarn introduces slight defect, however, an abnormal decrease in the lattice thermal
conductance per unit length is observed as the twist angle increases to ∼70°, indicating the phonon-soften
phenomenon when CNT is subjected to the torsion stress. The effective thermal conductivity is found to
increase linearly as porosity decreases when porosity is larger than 0.5, however, it is still an open question if
the linear relationship holds true for highly densified CNTYs.