Materials exist in nature in two principal forms as crystalline and non-crystalline (amorphous) solids, which differ substantially in their properties. In a crystal, the arrangement of atoms is in a periodically repeating pattern where as no such regularity of arrangement is found in a non-crystalline material. A crystalline solid can either be a single crystal, where the entire solid consists of only one crystal. or an aggregate of many crystal separated by well defined boundaries, in the latter form, the solid is said to be poly-crystalline. For crystalline solids sharp melting point, these are an-isotropic solids i.e., their properties are different in different directions. Whereas non-crystalline or amorphous solids are isotropic.
No comments:
Post a Comment