Thermoelectric Nanocomposites Prepared in High Voltage Electric Field
Mentor:Yong Gan, Associate Professor of Mechanical Engineering, California State Polytechnic University, Pomona
This work deals with manufacturing multicomponent organic/inorganic composite materials containing nanotubes, nanofibers and nanoparticles in electric field. The thermoelectric behavior of the composite materials is characterized. Conducting polymer (polyaniline) based multilayer composite nanofibers and nanorods were cast into carbon doped titania nanotubes. The titania nanotube template serves as the casting mold for the electric force assisted nanocasting. The self-organized titania nanotubes were made by electrochemical oxidation of pure titanium in a fluorine ion containing solution. High temperature heat treatment was conducted to dope carbon element into titania. The doped titania shows fairly high electrical conductivity. The polyaniline was mixed with thermoelectric Bi-Te alloy nanoparticles. The dispersion of the nanoparticles in the polymer nanorods was achieved via electric field assisted casting. The nanoparticles can enhance the thermoelectricity, specifically increase the Seebeck coefficient. Such nanorods have the low-dimensional complex structures, high interface areas for phonon scattering, leading to good thermoelectric properties of the composites, i.e. high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Structure analysis and Seebeck effect experiments were performed. The microstructure of the composite materials was studied using transmission electron microscopy. The diameter of the nanotube is about 150 nm and the length of the nanotube is about 3 microns. One of the fundamental problems associated with the manufacturing process is how fast the thermoelectric nanoparticles move into the titanium dioxide nanotubes under the electric force. The results were used to examine the effect of the manufacturing parameters on the production rate and the uniformity of the composite materials made in the casting process.