The Fraunhofer Institute for Ceramic Technologies and Systems IKTS developed a novel concept to produce thin-walled, one-sidedly closed tubes and similar geometries made of ceramics by highly productive extrusion. Thus, among others, the mass production of batteries becomes possible.
Extrusion is one of the most common shaping processes in technical ceramics. Preferably, it is used for the cost-effective production of axisymmetric components. Examples include honeycomb structures, tubes and profiles. The advantage of extrusion is the efficient production of complex structures in an endless strand. Challenges lie in delicate shapes with very thin wall thicknesses. In consideration of chemical and abrasion resistance, extruder construction, tool design and feedstock were perfectly matched at Fraunhofer IKTS. Additionally, the researchers conceptualized special removal and drying technologies, which prevent deformation of the designed components. The concept comprises a microwave drying with a special continuous dryer immediately adjoining the extruder mouthpiece in vertical extrusion.
For the production of the feedstock raw material mixtures were prepared for various functional materials and aqueously plasticized with organic excipients. For thin-walled extruded products the so-called "green strength", i.e. the dimensional stability of the green body after leaving the die, is of great importance. The feedstocks, specifically developed for thin-walled geometries, are characterized by a very good green strength.
Gundula Fischer, head of the extrusion competence center at Fraunhofer IKTS: "For the first time, a complete technology package for the production of thin and one-side closed ceramic geometries in a short cycle time can be offered due to our concept. For several highly interesting materials we have already demonstrated the capability, for example in electrolyte tubes that only now enable extremely cost-efficient batteries for the energy transition. With our equipment which includes various piston presses and auger extruders we are ready to realize customer projects."