Materials Technology

Structure of Materials

Structure of Materials• All materials are composed of atoms

Structure of Materials

The hydrogen atom

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.

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 eyeMagnified view – Large grains on sheet metal cause a rough surface

Structure of MaterialsInternal structure of typical

thermoplastic materials.

Aligned Molecules Branched Molecules

Aligned Molecules Branched Molecules

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

Structure of Materials

Internal structure of typical thermosetting plastics.

Cross-linked molecular chains

A cross-linked structure has adjacent chains linked by strong primary covalent bonds

Structure of MaterialsThe Body Centred Cubic Structure

BCC

Structure of MaterialsThe Face Centred Cubic Structure

FCC

Structure of Materials

Internal structure of typical hardwood

Structure of Materials

Internal structure of typical softwood