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Transmission Electron Microscopy Studies of Pd Encapsulation by Ceria-Zirconia Oxides

Published online by Cambridge University Press:  02 July 2020

J. C. Jiang ,
X. Q. Pan ,
G. W. Graham ,
R. W. McCabe  and
J. Schwank
J. C. Jiang
Affiliation:
Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI48109
X. Q. Pan
Affiliation:
Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI48109
G. W. Graham
Affiliation:
Chemical and Physical Sciences Laboratory, Ford Motor Company, MD3179/SRL., Dearborn, P.O. Box 2053, MI48121
R. W. McCabe
Affiliation:
Chemical and Physical Sciences Laboratory, Ford Motor Company, MD3179/SRL., Dearborn, P.O. Box 2053, MI48121
J. Schwank
Affiliation:
Department of Chemical Engineering, The University of Michigan, Ann Arbor, MI48109
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Extract

High-temperature catalysts containing Pd supported on high-surface area ceria-zirconia are optimum materials for fuel economy when automotive engines operate under high speed or load conditions. A prerequisite for developing such thermally stable catalysts is to gain a good understanding of the thermal deactivation modes contributing to the aging and degradation of catalysts in harsh thermal environments. It was discovered by X-ray diffraction that upon hightemperature aging, Pd may sinter into large (about 10 nm diameter) particles and become encapsulated in the ceria-zirconia. To confirm this conclusion, a prototype high-temperature catalyst containing Pd supported on high-surface area ceria-zirconia, aged at temperature above 1100 °C is studied by transmission electron microscopy (TEM).

The ceria-zirconia supported Pd (0.25 wt%) catalyst was aged at 1105 °C and calcined at 700 °C for 2 h. For TEM sample preparations, first of all, a large-size aggregate with diameter about 1 mm was selected and sandwiched between by two pieces of silicon crystal.

Type
Nanophase and Amorphous Materials
Information
Microscopy and Microanalysis , Volume 4 , Issue S2: Proceedings: Microscopy & Microanalysis '98, Microscopy Society of America 56th Annual Meeting, Microbeam Analysis Society 32nd Annual Meeting, Atlanta, Georgia July 12-16, 1998 , July 1998 , pp. 724 - 725
Copyright
Copyright © Microscopy Society of America

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References

1.Graham, G. W., Jen, H. -W., Chun, W., and MaCabe, R. W., Catal. Lett. 44 (1997) 185CrossRefGoogle Scholar