Modeling the Optical and Radiative Properties of Vertically Aligned Carbon Nanotubes in the Infrared Region

Abstract

During the past decade, research on carbon nanotubes has revealed potential advances in thermal engineering applications. The present study investigates the radiative absorption and reflection of vertically aligned carbon nanotubes (VACNTs) in the broad spectrum from the nearinfrared to farinfrared regions. The optical constants of VACNT are modeled based on the dielectric function of graphite and an effective medium approach that treats the CNT film as a homogenized medium. Calculated radiative properties show characteristics of nearunity index matching and high absorptance up to around 20 خ¼m wavelength. The packing density and degree of alignment are shown to affect the predicted radiative properties. The Brewster angle and penetration depth of VACNTs are examined in the infrared spectrum. The radiative properties for VACNT thin films are also evaluated, showing some reduction of absorptance in the nearinfrared due to transmission for film thicknesses less than 50 خ¼m. This study provides a better understanding of the infrared behavior of VACNT and may guide the design for its applications in energy harvesting, spaceborne detectors, and stealth technology.