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Unformatted text preview: A parameter if it results in
reduction in the total energy of the system. In the absence of energy reduction the reaction
the analysis converse is It may be used if reaction is thermodyns between atoms that are deﬁned not occur; however, the of creep. not true. That is, even ata a given stress to
determine how long the part will last at a given
r ions. Interstices in crystals arenamically possible, it may not actually occur. Thus, thermodynamics establishes the
necessary condition but not the sufﬁcient condition for a reaction to occur.
temperature or to determine the maximum allowable
Many chemical processes involve the breaking of atomic bonds and the subsequent
temperature materials. These changes in bond
formation of new bonds in for a ﬁxed time duration. structure can alter the
efect consisting of an atom or ion
properties of the material. Since changes in bond structure involve energy changes,
lattice Three-dimensional space-ﬁlling repeating comterstices of the structure under structural alterations are controlled by thermodynamic considerations. Examples ofpattern
on which atoms or the are placed to such
als may be either the same or a mon bond-alteration processes includeionsextraction of metals formasaaluminum, iron,
and titanium from their ores, the melting of a solid to form a liquid, chemical attack of
One formation in the three-dimensional
materials in lattice point
aggressive environments, theposition of a solid from a collection of isolated
space-ﬁlling repeating pattern that forms failure of materials
on A solid solution in which atoms, the degradation of polymers in ultraviolet light, and the a crystal. One or
resulting from the application of excessive force that breaks atomic bonds.
more atoms or ions are placed at each lattice point.
ign species are located in the
It is important to note that changes in the system variables can result in a change in the
thermodynamically favored state. For example, consider the change in bond calculate the
lever rule An equation that enables one to stru...
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