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Thermoplastic Forming as an Alternative Shaping Process for Near-Net-Shape Production of C-SiSiC Ceramics via Liquid Silicon Infiltration (LSI) Process
S. Weber1, F. Sommer2, F. Kern2, R. Gadow2, H. Voggenreiter1, D. Koch1
1 Institute of Structures and Design, Dep. Ceramic Composites and Structures, German Aerospace Center (DLR), Pfaffenwaldring 38 – 40, D-70569 Stuttgart, Germany
2 Institute for Manufacturing Technologies of Ceramic Components and Composites, University of Stuttgart, Allmandring 7b, D-70569 Stuttgart, Germany
received March 12, 2014, received in revised form May 7, 2014, accepted May 25, 2014
Vol. 5, No. 3, Pages 223-236 DOI: 10.4416/JCST2014-00011
Abstract
The present study demonstrated the feasibility of producing carbon-based green bodies by means of extrusion, pyrolysis and subsequent conversion to C-SiSiC ceramics according to the LSI process. A thermoplastic binder system was used for the development of feedstocks that differ from conventional duroplastic binder systems as these would have created difficulties during processing owing to their curing behavior. Activated carbon, carbon fibers and semi-coke were used as fillers and a source of a sufficiently stable carbon backbone in the carbonized intermediate. Special attention was paid to the characterization and quantification of material behavior at the water debinding step as well as at thermal treatment during pyrolysis. Porosity and microstructural characteristics of carbon bodies and subsequent C-SiSiC microstructure after Si-infiltration were investigated by means of scanning electron microscopy and porosity measurements. The feasibility of producing carbon-based extrusion feedstocks with high homogeneity and flowability which can be converted into SiC by means of LSI shows that the concept may be applied to production of near-net-shape C-SiSiC components by means of thermoplastic injection molding.
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Keywords
Extrusion, injection molding, SiC, porosity, feedstock system
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