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Is it true that ceramics are not always hard, brittle and insulating?

   

Frequently Asked Questions

The common properties exhibited by ceramic materials (a function of very strong ionic and covalent bonding) include: high strength (particularly in compression); thermal and electrical insulation; and low toughness.

However, the wider range of properties available from ceramic materials is not widely appreciated. For example:

  • Whilst ceramics are perceived as electrical and thermal insulators, ceramic oxides (initially based on Y-Ba-Cu-O) are the basis for high temperature superconductivity, i.e. the most electrically conducting materials known to man
  • Diamond, beryllia and silicon carbide have high thermal conductivities - comparable to aluminium and copper -

    MaterialThermal conductivity
    (W/m.k)
    Diamond 2000
    Beryllia 215
    Silicon carbide 270
    Aluminium 220
    Copper 315
  • Appropriate processing can overcome inherent stiffness to allow the production of ceramic springs
  • Monolithic ceramics such as zirconia and ceramic composites have been produced, with a fracture toughness about half that of steel - 20 compared with 50 MPa.m 0.5