Firing of ceramics

Sintering of Ceramics. The thermodynamics of the sintering process were presented in Section 2.2.2.4. We describe here some of the more practical aspects of sintering as they relate to the firing of ceramics and glasses. 

Fig. 9.12 Side elevation (schematic) of a directly flame heated tunnel kiln for the firing of ceramic parts and typical temperature profile [B.12c].

Most ceramic products are fired in air under oxidizing conditions. The ideal kiln for the firing of ceramics is capable of heating and cooling the parts uniformly at the maximum rate of temperature change for each of the stages mentioned in Tab. 6.7-6. 

If, as in burning lime or fusing porcelain enamel, the purpose is used to cause chemical reactions, specific heats and reaction heats should be obtained from chemical and ceramic engineering handbooks, such as references 16, 46, and 82. In the firing of ceramic materials, much heat also is required for driving out and evaporating moisture. 

In archaeological contexts TL is most commonly used to date the firing of ceramics (including the clay cores sometimes found in metal castings) and burnt stone (particularly flint). OSL is used mostly to date sediment deposits. 

The conclusion that can be drawn is that hybrid heating, which takes advantage of the volumetric nature of microwave heating, can allow faster, and consequently, lower energy and hence cheaper firing of ceramic components as well as yielding superior properties. 

Figure 1.18 Schematic indication of the distinction between densifying and nondensi-fying microstructural changes resulting from atom transport during the firing of ceramic powders.

Anon, (2000). The microwave-assisted gas firing of ceramics. Energy Efficiency Best Practice Programme Future Practice Profile 57, March. 

---