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Manufacturing of porous mullite fiber compacts by uniaxial hot pressing of semicrystalline MAFTEC® MLS-2 organic bound mats

Published online by Cambridge University Press:  29 June 2017

Peter Mechnich*
Affiliation:
German Aerospace Center (DLR), Institute of Materials Research, Köln 51147, Germany
Ferdinand Flucht
Affiliation:
German Aerospace Center (DLR), Institute of Materials Research, Köln 51147, Germany
Martin Schmücker
Affiliation:
German Aerospace Center (DLR), Institute of Materials Research, Köln 51147, Germany
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

Highly porous and fully crystalline mullite fiber compacts were fabricated by uniaxial hot pressing of stacked short-fiber mats without binders or sintering aids. The special feature of this new fabrication method is the use of MAFTEC® organic bound mat (OBM) type fiber mats consisting of semicrystalline “MLS-2” short fibers. In contrast to conventional polycrystalline mullite fibers, semicrystalline MLS-2 fibers consist of amorphous silica and nanoscale transitional alumina. Due to this special microstructure, MLS-2 fibers are less prone to fiber breakage upon shear load and therefore can well withstand pressure-assisted consolidation. Hot pressing of stacked OBM to highly porous fiber compacts is facilitated by the thermally driven softening of amorphous silica above 900 °C; favorable deformation and consolidation rates are achieved above 1050 °C. Above 1250 °C the mullite is crystallized at the expense of amorphous silica and simultaneously both deformation and consolidation comes to an end. Obtained MAFTEC OBM-derived fiber compacts consist only of crystalline mullites, and therefore mechanical properties are favorably retained at high temperatures.

Type
Invited Articles
Copyright
Copyright © Materials Research Society 2017 

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Footnotes

Contributing Editor: Eugene Medvedovski

References

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