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Graded Cellular Ceramics from Continuous Foam Extrusion

Authors

  • Bruno Ceron-Nicolat,

    1. Department of Materials Science – Glass and Ceramics, University of Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen, Germany
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  • Friedrich Wolff,

    1. Department of Materials Science – Polymer Materials, University of Erlangen-Nuernberg, Martensstrasse 7, D-91058 Erlangen, Germany
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  • Andrea Dakkouri-Baldauf,

    1. Department of Materials Science – Glass and Ceramics, University of Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen, Germany
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  • Tobias Fey,

    Corresponding author
    1. Department of Materials Science – Glass and Ceramics, University of Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen, Germany
    • Department of Materials Science – Glass and Ceramics, University of Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen, Germany
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  • Helmut Münstedt,

    1. Department of Materials Science – Polymer Materials, University of Erlangen-Nuernberg, Martensstrasse 7, D-91058 Erlangen, Germany
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  • Peter Greil

    1. Department of Materials Science – Glass and Ceramics, University of Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen, Germany
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  • The authors gratefully acknowledge the funding from DFG Cluster of Excellence “Engineering of Advanced Materials” at the University of Erlangen-Nuernberg.

Abstract

Cylindrical SiOC foam filaments with a radial gradient in pore cell size were processed by continuous extrusion foaming of a methyl polysilsesquioxane. Upon leaving the extrusion nozzle foaming was initiated by pressure release which caused precipitation of supersaturated carbon dioxide from the polymer filament. Rapid cooling of the thin filaments generates a radial gradient of melt viscosity which gives rise for formation of closed cell morphology of isotropic pore cells in the core (diameter < 200 µm) and non-isotropic pore cells near the sur-face (shell; <20 µm). After pyrolysis at temperatures ranging from 800 to 1400 °C the stabilized polymer gradient foams were converted into closed cell SiOC ceramic gradient foams. XRD reveals the SiOC residue to be amorphous up to 1200 °C whereas crystallization of ß-SiC was observed at 1400 °C. A superior compressive strength of 9 MPa and a Young´s modulus of 7 GPa at a relative density of 0.18 were measured at an optimum pyrolysis temperature of 1000 °C.

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