Silicate Ceramics

In the production of silicate ceramics, heat treatment contributes significantly to product quality and manufacturing costs. It is therefore worthwhile to optimise the process parameters during heat treatment.

For drying, binder burnout, quartz conversion and dewatering, processes have to be identified that allow the highest possible throughput on the one hand, but on the other hand ensure that the components are damage-free. During firing, the aim is to achieve near-net-shape production with narrow manufacturing tolerances and good material properties. For example, new designs can be realised with suitable firing conditions. For cost reasons, the throughput through the firing furnace should be maximised and its energy consumption and maintenance requirements minimised. The reject rate is to be minimised. Specific methods for process optimisation have been developed at Fraunhofer-Center HTL for this purpose.

Further Information


During drying, the water still contained in the shards must be removed without causing damage. Due to the small pores, considerable drying stresses can occur. Too rapid or uneven drying leads to cracks or warping. Here, the local drying rates are strongly dependent on the relative humidity, the temperature and the air flow.


Binder Burnout

If the mass contains organic additives, combustion heat is generated during their burnout. Inside the green parts, where the oxygen concentration is very low during binder burnout, pyrolysis reactions can take place at the same time, which consume heat. The resulting temperature differences cause thermal stresses, which in turn can lead to cracks or destruction of the green parts.


Dehydration takes place in silicate ceramics when the shards are heated to higher temperatures - between 500°C and 700°C, for example. During this process, the water of crystallisation contained in the clay raw materials is removed from the shards (dehydration). For example, kaolinite is transformed into metakaolin by dehydration.



When firing silicate ceramics, a compaction with defined residual porosity should be achieved. The microstructure should be free of defects and homogeneous, and the component must not warp. If glazes are used, they must be free of defects such as pinholes or bubbles.

Methods for Process Optimisation

The process optimisation methods used at the HTL are suitable for all types of silicate ceramics: porcelain, earthenware or stoneware and also silicate refractory materials. Small components can be optimised just as well as several-metre-long high-voltage insulators made of porcelain or pipes made of stoneware.


Other application and product areas

Aeronautics and Aerospace

Energy Technology