Module 1: Structure of Ceramics
  A Brief Review of Bonding in Materials
 


      1.2.1 Primary Bonding
      There are three types of primary bonding mechanisms: metallic, covalent and ionic       bonding.

Figure 1.9 Metallic Bonding

      1.2.1.1 Metallic bonding :

  • This kind of bonding is characterized by presence of a sea of electrons around atoms in metal giving rise to flexible bonds, good malleability, high electrical and thermal conductivity. Most metals such as Ni, Fe, Cu, Au, Ag etc exhibit this kind of bonding.

      1.2.1.2  Covalent Bonding:

  • In this bonding, atoms share their outer shell unpaired electrons leading to a stronger and directional bonding.

  • Examples of materials showing this bonding are mainly group IV elements and compounds such as Si, C, Ge, and SiC and gases like methane.

Figure 1.10 Schematic of covalent bonding

      1.2.1.3 Ionic Bonding :

  • This bonding occurs due to large differences in the electronegativities of two elements, for example in NaCl, MgO etc.

  • This type of bonding typically leads to high bond energies, high bond strength, high modulus, brittle nature, generally low thermal and electrical conductivities making them excellent insulators.
    Figure 1.11 Schematic of ionic bonding