<p> An investigation is reported of oxygen diffusion in monoclinic
zirconia at elevated temperatures. </p> <p> A method was developed for production of solid zirconia spheres
of a quality suitable for diffusion measurements. The spheres, 60μ
and 90μ diameter were subsequently used for the determination of the
coefficient of self-diffusion of oxygen in stoichiometric zirconia at
800°C, 850°C, 900°C, 950°C and 1000°C. Oxygen O18 isotope exchange
using mass spectrometry for the gas analysis was employed for this
investigation. </p> <p> The oxygen self-diffusion coefficent was found to conform to
the Arrhenius equation (see online text for equation) Theoretical considerations indicate that this diffusivity represents virtually the lattice diffusion of oxygen in zirconia. </p> <p> Diffusivities of oxygen in zirconia scale calculated from
zirconium oxidation studies are 104 times higher and are believed to
be due to short-circuit diffusion through line defects. To substantiate this hypothesis, "slabs" of stoichiometric zirconia scale and irregular,
but equiaxed particles of the same material were used for oxygen diffusion
experiments employing the same method. The diffusivities for the slabs
were 10^3 times higher than those for spheres, supporting the validity
of the short-circuit diffusion theory for zirconia scale. </p> <p> Oxygen concentration drop across zirconia scale on metal, during
its formation by parabolic kinetics was calculated for 600°C and 850°C,
and was found to be 0.04 g/cm3 approximately, while the concentration
drop across the interface between the oxide and the oxygen-saturated
metal was about 1.07 g/cm3. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19596 |
| Date | 08 1900 |
| Creators | Madeyski, Andrew |
| Contributors | Smeltzer, W. W., Metallurgy and Materials Science |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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