Basic material

• Crystalline solid


  Atoms, ions or molecules are arranged in an ordered and symmetrical pattern that is repeated over the entire crystal (crystal structure)
• Amorphous solid


  Atoms in the solid are arranged randomly, they do not have definite geometrical shape

  
• Classification of materials

  • Metal Alloys
  • Polymers
  • Ceramics
  • Composites
  • Biomaterials
• Properties of materials

  • Mechanical
  • Thermal
  • Electrical
• Material science


  A branch of science that focuses on materials; interdisciplinary field composed of physics and chemistry
• Material science


  Relationship of material properties to its composition and structure
• Material scientist


  A person who uses his/her combined knowledge of physics, chemistry and metallurgy to exploit property-structure combinations for practical use
• Unit cell


  The smallest repeating structure of a solid
• Types of unit cells

  • Cubic
  • Hexagonal
  • Tetragonal
  • Rhombohedral
  • Orthorhombic
  • Monoclinic
  • Triclinic
• Metallic crystal structure


  • Atomic bonding is metallic and nondirectional in nature
  • 3 simple crystal structures found for most of the common metals: FCC, BCC, HCP
• Face-centered cubic (FCC)


  Cubic geometry, with atoms located at each of the corners and the centers of all the cube faces
• Coordination number


  The number of nearest neighbour atoms or ions surrounding an atom or ion
• Coordination number for FCC is 12
• Atomic Packing Factor (APF)


  Measure of how efficiently atoms are packed in a crystal structure
• APF for FCC is 0.74
• Body-centered cubic (BCC)


  Cubic unit cell with atoms located at all eight corners and a single atom at the cube center
• Coordination number for BCC is 8
• APF for BCC is 0.68
• Total atoms in BCC unit cell is 2
• Hexagonal close-packed (HCP)


  Unit cell has a hexagonal base and atoms are arranged in a close-packed manner
• Total atoms in HCP unit cell is 6
• Coordination number for HCP is 12
• APF for HCP is 0.74
• Simple cubic (SC)


  Unit cell consists of atoms situated only at the corners of a cube
• None of the metallic elements have SC crystal structure due to its low APF of 0.54
• Amorphous solid


  Atoms are arranged randomly, they do not have definite geometrical shape

  
• Examples of amorphous solids

  • Glass
  • Rubber
  • Gels
  • Plastics
• Differences between crystalline and amorphous solids

  • Crystalline solids have well-defined geometrical shape, amorphous solids do not
  • Crystalline solids have sharp melting point, amorphous solids melt over a wide range
  • Crystalline solids have definite heat of fusion, amorphous solids do not
  • Crystalline solids are anisotropic, amorphous solids are isotropic
  • Crystalline solids are true solids, amorphous solids are pseudo solids

  
• Crystals are anisotropic