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Keenan, M., 1997. The influence of dopants on the surface properties of zirconia. PhD, Nottingham Trent University.
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Abstract
The surface area of zirconia is known to decrease dramatically upon heating. The addition of dopants to zirconia has been found to stabilize the surface area of zirconia against sintering. The dopants investigated were silica, lanthana and ceria, over the calcinations temperature range 400 to 1050°C. The surface area of pure zirconia decreases from 109 m2g-1 at 400°C to 15 m2g-1 at 900°C ( it has a surface area < 3 m2g-1 at 1050°C), whereas, 3.5wt% SiO2/ZrO2 has a surface area of 170 m2g-1 at 400°C and 13 m2g-1 at 1050°C. The addition of 3mole% lanthana stabilized the surface area to a similar amount as silica but the addition of ceria did not stabilize the surface area against sintering.
Varying the nature of the preparation of the mixed oxides determined the phase of the sample. Coprecipitation preparation stabilized the tetragonal phase of zirconia up to 1050°C whereas, impregnation preparation stabilized the monoclinic phase of zirconia up to 900°C. The phase composition was identified using powder x-ray diffraction.
The catalyst surface was characterized using x-ray photoelectron spectroscopy. Enrichment of the surface with the dopant was observed with increasing calcinations temperature.
From the catalytic decomposition of propan-2-ol test reaction, the addition of dopants altered the surface properties of pure zirconia. Zirconia produced the acid product in the reaction whereas, silica doped zirconia showed enhanced acidity, lanthana doped zirconia showed basic activity and the addition of ceria suppressed the catalytic activity. From the decomposition reaction, the enhanced acidity of silica doped zirconia was investigated using combined Fourier transform infrared spectroscopy and pyridine adsorption. The results showed that the catalytic activity was taking place at Lewis acid sites.
| Item Type: | Thesis | ||||
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| Creators: | Keenan, M. | ||||
| Date: | 1997 | ||||
| ISBN: | 9781369325270 | ||||
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| Divisions: | Schools > School of Science and Technology | ||||
| Record created by: | Linda Sullivan | ||||
| Date Added: | 24 Jun 2021 15:57 | ||||
| Last Modified: | 13 Dec 2023 13:56 | ||||
| URI: | https://irep.ntu.ac.uk/id/eprint/43222 |
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