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Institut für Polymerchemie |
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Lehrstuhl für Makromolekulare Stoffe und Faserchemie |
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Prof. Dr. Michael R. Buchmeiser
Oxide Ceramic Fiber Development at ITCF Denkendorf |
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Oxide Ceramic Fiber Development at ITCF Denkendorf
Ceramic fibers are key components for ceramic fiber-reinforced composites (CMCs), which form a new class of light-weight high temperature
resistant materials with exceptional properties such as non-brittle fracture behavior, resistance against extreme thermo-shocks and very good corrosion
resistance. These materials are predestined for many applications in technical fields like aerospace, power engineering and automotive but have also
potential in medical fields like bone reconstruction and tissue engineering.
Fundamental research in the field of oxide ceramic fibers started at ITCF Denkendorf as early as in 1989. The complete production process of this fiber type
has been studied intensively comprising the development of spinning dopes, the dry spinning process as well as pyrolysis and sintering. Both alumina and mullite
type fibers with excellent high temperature properties have been developed. Currently, the transfer of the technology into industrial scale is under progress.
New developments focus on the improvement of creep resistance and the reduction of grain growth in long time applications of oxide fibers, i.e. YAG fibers
(yttrium aluminum garnet) and structure-optimized alumina fibers (ZTA, zirconia toughened alumina). Another research field is the production of fibers, e.g.,
of Ca-phosphates, and of the corresponding scomposite materials for medical applications.
YAG fibers
Oxidic ceramic fibers are a fundamental component of high-temperature resistant fiber-matrix composites and are increasingly used in
rockets, combustion chambers and engines, gas turbines, etc., thereby replacing highly legated steel. Generally, the creep rate of
polycrystalline ceramic fibers increases with decreasing grain size and the creep resistance of these fine-grained fibers is not very
high in contrast to their strength. Particularly under mechanical stress and at high temperatures exceeding 1100°C, they tend to
creep and brittleness increases due to grain growth, which can ultimately lead to failure of the entire device. Yttrium-Aluminum-Garnet
(YAG) fibers are high performance fibers with outstanding features such as high temperature stability, high modulus and strength, high
oxidation resistance and excellent creep resistance. As YAG is characterized by a very high melting point of almost 2000°C it is very
attractive for high temperature applications. Furthermore, it is chemically inert in reducing and oxidizing atmosphere and it is the
oxide with the highest creep resistance. For these reasons, YAG fibers satisfy the growing requirements especially in terms of chemical
and mechanical stability in long-term, high-temperature applications in oxidizing atmospheres and are therefore the most promising
materials to outperform the so far developed ceramic fibers in this area.
References:
- Ceramic Filament Fibers - A Review, D. Schawaller, B. Clauß, M. R. Buchmeiser, Macromol. Mater. Eng., 297, 502-522 (2012)
- Synthesis and Structural Investigation of Precursors for Non-Oxide Fibers,
B. Clauß, D. Schawaller, K. Meyer, J. Heck, O. Tsetsgee, K. Müller, M. R. Buchmeiser
in „High Temperature Ceramic Materials and Composites“, Proc. 7th Int. Conf. on High
Temperaure Ceramic Matrix Composites (HT-CMC7), Sept. 20-22, Bayreuth, Germany, p. 16-26; ISBN 978-3-00-032049-1
All research topics
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