last lecture

1
last lecture

• Introduction to materials science and engineering
• Atoms / electron configuration

2
today

• Bonding in solids
• Structure of crystal solids

3
Bonding Forces and Energies
distance r
4
The Periodic Table
increasing electronegativity
INTERMEDIATE
NONMETALS
METALS
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Ionic Bonding Covalent Bonding
e.g. sodium chloride
e.g. methane
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Metallic Bonding
7
Bonding Energies
8
Crystalline Structures
9
Crystalline Structures
amorphous
crystalline
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Example Glass
O2-
Si4
quartz (crystalline)
quartz glass (amorphous)
glass (amorphous)
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Crystalline Structures
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Hexagonal Crystal Structures
hcp unit cell
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Stacking Sequence of Close-Packed Structures
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FCC and BCC Solid Sphere Model
fcc unit cell
bcc unit cell
a
a
R
R atomic radiusa unit cell length / lattice
constant
15
Crystalline Structures of Materials
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Lattice Parameters
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Crystal Systems
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Crystal Systems
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How to define a direction

• Vector of convenient length (pass through origin)
• Project the vector to the axes (and measure in a,
  b, and c)
• Multiply or divide these numbers by common factor
  to get smallest set of integers
• Write them down as uvw

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Miller Indices Crystallographic Directions
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Miller Indices Crystallographic Directions
(Miller Bravais)
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How to define a plane

• Plane may not include origin!
• Determine the intercepts with appropriate axes as
  a, b, and c
• Take reciprocals (no intercept means infinity ?
  reciprocal of infinity 0)
• Multiply or divide these numbers by common factor
  to get smallest set of integers
• Write them down as (hkl)

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Miller Indices Lattice Planes
intersection points 1/2 a, 1/2b, 1/2c reciprocal
values (222)
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Defects

• Point defects
• Linear defects
• 2-dimensional defects

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Point Defects
self-interstitial
vacancy
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Impurity Atoms
interstitial
substitutional
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Dislocations Edge Dislocation
inserted half plane
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Dislocations Screw Dislocation
dislocation line
Burgers vector
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Grain Boundaries
high-angle grain boundary (Qgt15)
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next

• Properties of materials