Submitted By Sadawa2344124
• Have you ever wondered how atoms assemble into solid structures? • How does the density of a material depend on its structures?
• Solid materials can broadly be classified as crystalline and non crystalline (amorphous) solids. • In crystalline solid the arrangement of atoms is in a periodically repeating manner whereas no such patterns are found in a non-crystalline solid.
• 2 types of crystalline solids: a) Single crystal : the periodic and repeated arrangement of atoms is perfect or extends throughout the entirety of the specimen without interruption. b) Polycrystalline solid : a collective aggregate of many crystals separated by well defined boundaries.
• As a general rule, most metals are crystalline, while ceramics and polymers may be either crystalline or non-crystalline.
Differences between crystalline and non-crystalline solids
Regular and orderly manner in all three dimensions
Fracture mechanism Ductile manner. Solids Brittle manner. behave elastically up to Solids do not their yield points behave elastically
• A crystalline solid consists of a number of crystals. A crystal structure can be considered as consisting of tiny blocks which are repeated in three dimensional pattern. • Each of the tiny block (called a unit cell) is actually made from the arrangement of a small group of atoms.
• Types of crystal structure: 1) Simple cubic 2) Body centered cubic (BCC) 3) Face centered cubic (FCC) 4) Hexagonal closed packed (HCP)
BODY-CENTERED CUBIC CRYSTAL STRUCTURE
FIGURE 3.2 For the body-centered cubic crystal structure,…...