High-temperature resistant ceramic fibers – from this special field of research the DITF have already reported several times on new developments. A new type of oxide ceramic fibers, whose properties redefine the leading standard, can now be presented as the result of intensive research work.
The outstanding fiber properties relate to ceramics made of zirconium oxide-reinforced mullite. This ceramic class could be spun and sintered continuously in the form of fibers for the first time. Ceramic fibers are used to produce fiber-reinforced ceramic materials. These materials are resistant to thermal shock and are suitable for technical use at particularly high temperatures. For these applications, the ceramic fibers must have a ceramic microstructure that remains stable even under these extreme conditions.
While ceramic fibers made of mullite have already met these requirements in the best possible way for some time and have become established in many technical applications, the newly presented material from the DITF expands the technical possibilities. For the first time, it has been possible to produce mullite fibers with a zirconium oxide content of 3 to 15 percent by weight. The addition of zirconium oxide leads to the formation of a novel ceramic microstructure that exhibits improved mechanical properties compared to pure mullite.
Even though the exact mechanisms of action of the zirconium oxide additive in the fibers still have to be elucidated, it is known from “normal” ceramics that mechanical properties, especially fracture toughness, can be improved by producing such dispersion structures from several components. That this can also be transferred to ceramic fibers has already been shown by the very promising results of mechanical investigations. The production of zirconium oxide-reinforced ceramic fibers builds on decades of expertise at the DITF within the Competence Center High Performance Fibers headed by Dr. Bernd Clauß. Nevertheless, a completely new orientation of the process steps in fiber production was necessary. From the production of the spinning mass via the dry spinning process to the difficult adjustment of temperature profiles in the burning steps of calcination and sintering, the production process had to be realigned. In the process, the ceramic system of zirconium oxide-reinforced mullite was researched from the ground up. The findings were incorporated into the technical optimization of the process control, and a patent application was filed for the material and process.
For the technical application of the novel fibers, a significant improvement of materials in specific areas such as high-temperature lightweight construction or chemical process engineering is expected. In addition, the so-called fiber ceramics will play a major role in many high-temperature processes in the fields of mobility and energy in the future.
