Semester

Summer

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Daneesh Simien

Abstract

Single-walled carbon nanotubes (SWNTs) are comprised entirely of carbon atoms which lie in a graphitic plane rolled into a seamless cylinder. The direction in which the graphic plane is rolled affects the subsequent chiralities of the SWNTs. This direction is called the chiral vector. This chiral vector, Ch =na1+ma2, is described in terms of a pair of integers (n,m) and a pair of lattice vectors (a1,a2) associated with each carbon atom in the graphene sheet. The magnitude of the chiral vector determines the diameter of the nanotubes as d= Ch/pi. SWNTs with integers n-m =3i, where i = 0, 1, 2, 3.... are metallic at room temperature, while those with n-m =3 i+1 and n-m=3i+2 are semiconducting at room temperature.;SWNTs are being incorporated into a myriad of materials for applications ranging from biosensors to nanoscale electronics to structural materials. The ability to produce SWNTs with well defined chiralities will enable us to conduct more fine tuned experiments with even better reproducibility of our results. As-produced SWNTs grown using the most common synthesis methods of arc discharge, laser ablation and chemical vapour deposition techniques, each render nanotube powders with varying amounts of catalysts and uniformly presents SWNTs with a variety of chiralities and lengths. None of these procedures has yet to produce a single chirality SWNT powder, therefore developing techniques to produce monodispersed SWNT fractions via post-synthetic approaches are essential to have truly reproducible studies where SWNT are incorporated. In this thesis, we present our efforts to sort cobalt molybdenum catalyst grown nanotubes (CoMoCAT) by chirality, which are rich in (6,5) nanotubes species, identifying homogeneous fractions of single chirality (6,5) nanotubes and a secondary mixed layer of (6,5) and (7,5) using density gradient ultracentrifugation techniques. Additionally these individualized species were deposited as random network thin films on cellulose ester membranes and evaluated for their critical percolations concentration (onset of electrical conductivity), and surface conductivity using the Generalized Effective Media (GEM) model.

Download

Share

COinS