1. MECHANICAL PROPERTIES OF CERAMICS AND ITS APPLICATION

2. MECHANICAL PROPERTIES OF CERAMICS Flexural Strength The stress at fracture using this flexure test is known as the flexural strength. Flexure test :which a rod specimen having either a circular or rectangular cross section is bent until fracture using a three- or four-point loading technique

3. For a rectangular cross section, the flexural strength σ fs is equal to, L is the distance between support points When the cross section is circular, R is the specimen radius Stress is computed from, specimen thickness the bending moment the moment of inertia of the cross section MECHANICAL PROPERTIES OF CERAMICS

4. Hardness Hardness implies a high resistance to deformation and is associated with a large modulus of elasticity. In metals, ceramics and most polymers, the deformation considered is plastic deformation of the surface. For elastomers and some polymers, hardness is defined at the resistance to elastic deformation of the surface. Technical ceramic components are therefore characterised by their stiffness and dimensional stability. Hardness is affected from porosity in the surface, the grain size of the microstructure and the effects of grain boundary phases.

5. MECHANICAL PROPERTIES OF CERAMICS Elastic modulus The elastic modulus E [GPa] of almost all oxide and non-oxide ceramics is consistently higher than that of steel. This results in an elastic deformation of only about 50 to 70 % of what is found in steel components. The high stiffness implies, however, that forces experienced by bonded ceramic/metal constructions must primarily be taken up by the ceramic material.

6. MECHANICAL PROPERTIES OF CERAMICS Density The density, ρ (g/cm³) of technical ceramics lies between 20 and 70% of the density of steel. The relative density, d [%], has a significant effect on the properties of the ceramic.

7. MECHANICAL PROPERTIES OF CERAMICS Porosity Technical ceramic materials have no open porosity. Porosity can be generated through the appropriate selection of raw materials, the manufacturing process, and in some cases through the use of additives. This allows closed and open pores to be created with sizes from a few nm up to a few µm. Change in elastic modulus with the amount of porosity in SiOC ceramic foams obtained from a preceramic polymer

8. MECHANICAL PROPERTIES OF CERAMICS Strength The figure for the strength of ceramic materials, [MPa] is statistically distributed depending on the material composition the grain size of the initial material and the additives the production conditions the manufacturing process Strength distribution within batches

9. MECHANICAL PROPERTIES OF CERAMICS Toughness Ability of material to resist fracture affected from, temperature strain rate relationship between the strenght and ductility of the material and presence of stress concentration (notch) on the specimen surface

10. APPLICATION OF CERAMIC Compressive strength makes ceramics good structural materials (e.g., bricks in houses, stone blocks in the pyramids) High voltage insulators and spark plugs are made from ceramics due to its electrical conductivity properties. Good thermal insulation has ceramic tiles used in ovens and as exterior tiles on the Shuttle orbiter Some ceramics are transparent to radar and other electromagnetic waves and are used in radomes and transmitters

11. Hardness, abrasion resistance, imperviousness to high temperatures and extremely caustic conditions allow ceramics to be used in special applications where no other material can be used Chemical inertness makes ceramics ideal for biomedical applications like orthopaedic prostheses and dental implants Glass-ceramics, due to their high temperature capabilities, leads to uses in optical equipment and fibre insulation