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Unformatted text preview: Chapter 3 Structures of Metals and Ceramics Fundamental Concepts Crystalline material = one in which the atoms are situated in a repeating or periodic array over large atomic distances o That is long range order exists such that upon solidification, the atoms position themselves in a repetitive 3-D pattern, in which each atom is bonded to it nearest neighbor atom Amorphous materials = materials that do not crystallize Some properties of crystalline solids depend on the crystal structure of the material Crystal Structure = the manner in which atoms, ions, or molecules are spatially arranged Atomic hard-sphere model = spheres representing the nearest-neighbor atoms touch one another o Used to describe crystalline structures, atoms (or ions) are thought of as being solid spheres having well-defined diameters Lattice = 3-D array of points coinciding with atom positions (or sphere centers) Unit Cells Atomic order in crystalline solids indicates that small groups of atoms form a repetitive pattern Unit cells = subdivide the structure into small repeating entities o Unit cells for most crystal structures are parallelepipeds having 3 parallel faces o Represent the symmetry of crystal structure Metallic Crystal Structure...
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This note was uploaded on 10/02/2011 for the course ENME enme382 taught by Professor Bruck during the Fall '10 term at Maryland.
- Fall '10