Chapter_03.pdf

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Chapter 3
Structures of
Metals and Ceramics
¤ How do atoms assemble into solid structures?
¤ How do the structures of ceramic
materials differ from those of metals?
¤ How does the density of a material depend on
its structure?
¤ When do material properties vary with the
sample (i.e., part) orientation?
ENERGY AND PACKING
Now, bonding energy is not only between two atoms, its from many atoms.
Dense, regular-packed structures tend to have lower energy.
¤ Non dense, random packing
Energy
typical neighbor
bond length
typical neighbor
bond energy
r
average
Energy
¤ Dense, regular packing
typical neighbor
bond length
r
typical neighbor
bond energy
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Building 3D ‘ordered’ array of atoms for Dummies
(i) Construct lattice
(ii) Filling the lattice
with atoms or
molecules or group
of atoms/molecules
You could choose many
number of different unit
cells for the same building
process.
1079541174.018.png
7 Crystal Systems
&
14 Crystal Lattices
Any crystalline structure (3D ordered array of atoms/molecules)
must fall into one of the systems and one of the crystal lattices.
1079541174.019.png
Often called ‘lattice constants’
Unit cells
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