Thermal Conductivity of Carbon Nanotubes with Defects

The high thermal conductivities of carbon nanotubes (CNTs) measured experimentally and predicted from theory suggest that they are good candidates for next-generation thermal management materials. The quantities of CNTs needed in applications preclude the use of pristine products. Limited work, however, has been done to study thermal transport in CNTs with defects. In this paper, the thermal conductivities of pristine CNTs and CNTs with various defect types (adatoms, single vacancies, double vacancies, and Stone-Wales) are systematically predicted using molecular dynamics simulation and a direct application of the Fourier law. We investigate the correlation between the thermal conductivity and defect energy. INTRODUCTION The high thermal conductivities of carbon nanotubes (CNTs) measured experimentally [1–5] and predicted from theory [6–12] suggest that they are good candidates for nextgeneration thermal management materials. Defects in CNTs can be generated during growth, purification, and device production [13]. Recent experiments demonstrated that electron or ion plasma can be used to tailor the structure and properties of CNTs by introducing defects with precision [14]. These naturally or artificially induced defects inevitably change the mechanical, electrical, chemical, and thermal properties of CNTs. A few molecular dynamicsand first principles-based studies have predicted that thermal conductivity decreases as the defect concentration ∗Address all correspondence to this author. increases [6, 15–18]. However, most of these predictions were for CNTs with length less than 100 nm. Phonon transport in such CNTs is partially ballistic and the thermal conductivities are thus length dependent. Moreover, the relative impact of various defect types on thermal transport remains unclear. Understanding how topological defects modify phonon transport in a CNT is an important step in predicting how CNT-based materials or devices will behave in heat transfer applications. In this paper, we systematically investigate the thermal conductivities of pristine CNT and CNTs with various defect types (adatoms, single vacancies, double vacancies, and Stone-Wales) using molecular dynamics simulation and a direct application of the Fourier law. SIMULATION SETUP Thermal conductivity, k, is defined by the Fourier Law: