| Abstract: | Polyacrylonitrile based electrospun carbon nanofibers (CNFs) were used as a resistive type gas sensor to detect the adsorption of NO²́² gas. In an attempt to enhance the sensitivity CNFs to NO²́² for use in non-destructive leak testing, mesoporous structures were induced within the CNFs in order to increase the specific surface area of the fibers. This was done by including a sacrificial polymer, poly methyl(methacrylate), into the precursor solution used in the electrospinning process. Both porous and non-porous CNFs were manufactured in the lab using an electrospinning, stabilization, and carbonization method. These two sensor types were repeatedly tested in vacuum for sensitivity to the NO²́², and the non-porous sensors were found to be more sensitive. Characterization of both types of sensors followed in order to elucidate the mechanism that caused the porous fibers to have decreased sensitivity. The characterization included the bandgap measurements, chemical characterization of the functional groups and detailed porosity measurements. The sensitivity drop in the porous CNFs was explained in terms of their lower nitrogen content relative to pCNFs. In other words, adsorption of NO²́² gas onto the surface of the sCNF samples is assisted along by their extra nitrogen content relative to pCNFs, For all samples tested, the absorption of NO²́² gas would lead to more holes within the p-type semiconductor as the gas molecules binds electrons to surface, causing an increase in the hole density, and thus an increase in electrical conductivity of the samples. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/198146 |
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