MEPX
Chapter 2 of 10All chapters
  1. 1Describing a material
  2. 2Structure decides behaviour
  3. 3Metals
  4. 4Ceramics and polymers
  5. 5Composites
  6. 6How materials fail
  7. 7Processing changes properties
  8. 8Choosing a material
  9. 9Modern materials
  10. 10Materials and sustainability

Chapter 2 of 10

Structure decides behaviour

Atoms, crystals and defects.

Arrangement

Metals form crystals of repeating atoms. Glass is amorphous, with no long-range order. Polymers are long chains that tangle. The arrangement, not the element, dominates behaviour.

  • The same carbon makes graphite and diamond, differing only in arrangement.
  • Grain boundaries in metals block movement and raise strength.

Defects are useful

Real crystals contain dislocations, and metals deform because those dislocations move. Strengthening a metal is mostly the art of making them harder to move.