Breviary Technical Ceramics




Cordierite materials and others based on it are magnesium aluminosilicates, fabricated by sintering soapstone or talcum with the addition of clay, kaolin, fireclay, corundum and mullite. A simplified approximation to the composition of pure ceramic cordierite is approx. 14 % MgO, 35 % Al2O3 and 51 % SiO2.

Figure 5: Microstructure of a porous cordierite (C 520)

Cordierite materials have a low coefficient of thermal expansion. This is the reason for their outstanding thermal shock resistance combined with good mechanical strength. Two types of cordierite, porous and dense, are distinguished. The porous type has a low bending strength but even higher thermal shock resistance than the dense type, since it can absorb mechanical stresses in its porous structure.
Cordierite materials, moreover, behave inertly towards heating element alloys at temperatures up to 1,000°C or even 1,200 °C (there is no reaction between the heating element and the ceramic).

For this reason, cordierites are often found in electric heating applications, and in heat engineering in general.
Applications include, for example, insulators for continuous flow electric water heaters, heating element pipes, heating element supports in furnaces, link heaters, heating cartridges for soldering irons, gas heater inserts, spark protectors and catalyst carriers in automobiles.

For special purposes a material is available containing cordierite and mullite and having a high aluminium oxide content (C 530) which, for instance, permits higher application temperatures.

Aluminium- und Magnesiumsilikate (C 500)


<< back   home   next >>