09-09-Lecture

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

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Unformatted text preview: 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] CRYSTALLOGRAPHIC DIRECTIONS -...
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This note was uploaded on 03/26/2008 for the course ENGR 213 taught by Professor Dr.stubbs during the Fall '04 term at Texas A&M.

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

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