Real Materials

Surfaces, Grain Boundaries, and Interfaces

� These are two-dimensional defects that separate regions of ordered single-crystal structure, crystalline and amorphous regions, or different phases.
� A bubble raft model of grain boundaries is shown below.

� The bubbles mimic atoms in a polycrystalline solid and their arrangement near the grain boundaries indicates the variable interatomic spacing in these regions.
� The lower the angle between equivalent planes in adjacent crystallites the less disorder occurs in the boundary.