Page 133 - Materials Science and Engineering An Introduction
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C h a p t e r 4 Imperfections in Solids
(a) Schematic diagram showing
the location of the catalytic Atomic defects are
converter in an automobile’s responsible for reductions of
exhaust system. gas pollutant emissions from
today’s automobile engines.
A catalytic converter is the
(a) pollutant-reducing device that
is located in the automobile’s
exhaust system. Molecules of
pollutant gases become
attached to surface defects of
crystalline metallic materials
:
found in the catalytic
converter. While attached
to these sites, the molecules
(b) Schematic diagram
experience chemical reactions
of a catalytic converter.
that convert them into other,
non-polluting or less-polluting
substances. The Materials of
Importance box in Section 4.6
contains a detailed description
of this process.
(c) Ceramic monolith on
(b)
: which the metallic catalyst
substrate is deposited.
(c)
(d) High-resolution transmission electron micrograph
that shows surface defects on single crystals of one
material that is used in catalytic converters.
[Figure (a) from W. J. Stark, L. Mädler, M. Maciejewski, S. E. Pratsinis, and A.
Baiker, “Flame-Synthesis of Nanocrystalline Ceria/Zirconia: Effect of Carrier Liquid,”
Chem. Comm., 588–589 (2003). Reproduced by permission of The Royal
(d) Society of Chemistry.]
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