09-09-Lecture - ENGR 213 Structures of Metals and Ceramics 1 Types of Solids crystalline solids long-range order repetitive structure metallic ionic

09-09-Lecture - ENGR 213 Structures of Metals and Ceramics...

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1 ENGR 213 Structures of Metals and Ceramics
Types of Solids crystalline solids long-range order, repetitive structure metallic, ionic bonding (non-directional) metals, many ceramics, some polymers amorphous / non-crystalline solids short-range order, random & complex structure covalent bonding (directional)
CRYSTAL STRUCTURE lattice - 3D array of points (atom center) unit cell smallest repetitive structure defines crystal structure “building block” of a crystal chosen for maximum geometrical symmetry 7 crystal systems
EXAMPLE STRUCTURE
UNIT CELL GEOMETRY
6 CRYSTAL SYSTEMS Seven types Differ by Side lengths Angles Examples Cubic Equal Sides 90deg angles Hexagonal a = b c al = be = 90; gam =120
CRYSTALLOGRAPHIC DIRECTIONS - DIRECTIONAL INDICES vector through origin length projections on each axis in terms of unit cell dimensions smallest integers over bar indicates negative [u v w] [100] [010] [001]

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