Materials Technology Structure of Materials

1. Materials Technology • Structure of Materials

2. Structure of Materials Structure of Materials • All materials are composed of atoms The hydrogen atom

3. Structure of Materials • The arrangement of atoms within a material greatly influences that materials behaviour and properties e.g. • Hardness • Ductility • Malleability • Conductivity • Melting point, etc.

4. Structure of Materials • When metals solidify from a molten state the atoms configure themselves in an orderly arrangement called crystals. When formed this is called the crystalline (lattice) structure. • The smallest group of atoms showing this lattice structure is called the unit cell. The crystals begin to form independently at random locations Crystals continue to grow as solidification continues Note that the orientation of each site is different Fully solidified metal showing individual grains and grain boundaries The grains of zinc on the surface of galvanized steel are visible to the naked eye Magnified view – Large grains on sheet metal cause a rough surface

5. Structure of Materials • Internal structure of typical thermoplastic materials. During polymerisation the monomers are linked together by strong primary covalent bonds (sharing electrons) Adjacent chains are held together by weak Van der Waals forces Aligned Molecules Branched Molecules Aligned Molecules Branched Molecules

6. Structure of Materials • Internal structure of typical thermosetting plastics. A cross-linked structure has adjacent chains linked by strong primary covalent bonds Cross-linked molecular chains

7. Structure of Materials • The Body Centred Cubic Structure • BCC

8. Structure of Materials • The Face Centred Cubic Structure • FCC

9. Structure of Materials • Internal structure of typical hardwood

10. Structure of Materials • Internal structure of typical softwood