Browsing by Author "Featherstone, Graham Anthony"

In this thesis, the synthesis of titanium dioxide and sodium doped titanium dioxide nanofibers was undertaken through the use of the relatively new methods of solution blow spinning and electroblowing. These techniques are initially compared to other modern methods of nanofiber synthesis such as electrospinning, drawing, melt spinning and dry spinning. These techniques are evaluated based on production rate and the diameter of the formed nanofibers. This comparison shows that electroblowing and solution blow spinning are efficient high throughput methods for the formation of unordered nanofiber mats with diameters similar to those obtained in electrospinning. The formation of titanium dioxide nanofibers due to its role as a catalyst was of particular interest. Solution blow spinning and electroblowing are methods which employ the use of a high-velocity gas in order to stretch and elongate a viscous polymeric solution. While solution blow spinning relies entirely on the use of high-velocity gas, electroblowing additionally charges the elongated nanofibers which aids in the collection of the spun fibers, and this also affects the morphology of the final nanofibers. Inorganic nanofibers are obtained by adding a titanium dioxide precursor to the polymeric solution, which, upon calcination, forms solid titanium dioxide nanofibers. Dopants may also be added to the solution which allows for the formation of doped titanium dioxide nanofibers. Various solution and process parameters were studied in-depth in order to develop a full understanding of their effects on the diameters of the synthesized nanofibers. These parameters include the pressure of the gas, the feed-rate of the polymeric solution through the needle tip, the voltage applied to the needle tip, the concentration of the polymer and the distance from needle to the collector. After process and solution optimization, production rates of 0.39 g/h and 0.55 g/h were obtained for the titanium dioxide and sodium doped titanium dioxide nanofibers, respectively. With these optimized parameters, the average titanium dioxide fiber diameters measures 182 nm while the average sodium doped titanium dioxide diameters measured 184 nm. Crystallization studies were also conducted on the calcinated nanofibers. Both high-temperature in situ XRD studies as well as room temperature measurements on calcinated samples were done in order to cross-compare results and eliminate any errors associated with each individual method. The titanium dioxide nanofibers demonstrated a very defined crystallinity in which the fibers shifted from anatase to a predominantly rutile phase between the temperatures of 410 to 1050 °C. However, the sodium doped fibers demonstrated a mixed phase crystallinity in which no crystal structure was discernible.