Abstract

This work chronicles the fabrication of two unique thin films using carbon nanotubes. The first is a carbon film made primarily from vertically grown carbon nanotubes (CNTs) and rolled into lateral alignment. The second is an insulating film created by CNTs as a scaffolding to create a porous silica layer. Each topic represents a different method of utilizing CNTs for thin-film fabrication.Investigation of an entirely carbon thin film, comprised of aligned and laterally oriented carbon nanotubes was performed. The thin film was strengthened by deposition of amorphous carbon for a total thickness of <<> 5 Âµm. This thickness is thinner than many previous films fabricated entirely out of carbon. Vertically aligned CNT arrays were manually rolled into a thin sheet and released from the growth substrate. Infiltration with amorphous carbon (as carbon coating) on the rolled CNTs was used to improve adhesion between neighboring CNTs after lateral alignment and to improve the mechanical integrity of the film. Mechanical property characterization indicated the ability to sustain a pressure differential across the film of up to 82.7 kPa for a suspended film of 4 mm in diameter. Peak stress, Youngs modulus and biaxial modulus were obtained as a characterization of the strength of the thin film.Fabrication and examination of a porous silica thin film, potentially for use as an insulating thermal barrier, was investigated. A vertically aligned CNT forest, created by chemical vapor deposition (CVD), was used as a scaffolding for the porous film. Silicon was deposited on the CNT forest using low pressure CVD (LPCVD), then oxidized to remove the CNTs and convert the silicon to silica “ a material often used for electrical or thermal passivation. This fabrication method introduces hollow pores where the CNTs once occupied, further increasing the materials insulating properties. Thermal testing was performed by equating radiative and conductive heat transfer in a vacuum chamber and comparing the temperature difference between the film and a reference sample of comparable thermal resistance. For films approximately 50 Âµm thick, the thermal conductivity was found to be 0.054 - 0.071 W/mK.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering