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Open AccessFeature PaperArticle

Optimization and Characterization of Preceramic Inks for Direct Ink Writing of Ceramic Matrix Composite Structures

1
Department of Industrial Engineering, University of Padova, 35131 Padova, Italy
2
Department of Civil, Environmental and Architectural Engineering, University of Padova, 35131 Padova, Italy
3
Materials Science and Engineering, The University of Pennsylvania, State College, PA 16801, USA
*
Author to whom correspondence should be addressed.
Materials 2018, 11(4), 515; https://doi.org/10.3390/ma11040515
Received: 19 January 2018 / Revised: 17 March 2018 / Accepted: 23 March 2018 / Published: 28 March 2018
(This article belongs to the Special Issue Polymer Derived Ceramics and Applications)
In a previous work, an ink based on a preceramic polymer, SiC fillers, and chopped carbon fibers was proposed for the production of Ceramic Matrix Composite (CMC) structures by Direct Ink Writing (DIW) and subsequent pyrolysis. Thanks to the shear stresses generated at the nozzle tip during extrusion, carbon fibers can be aligned along the printing direction. Fumed silica was added to the ink in order to enhance its rheological properties; however, the printed structures still showed some deformation in the Z direction. In this work, a second ink was successfully developed to limit deformation and at the same time avoid the addition of fumed silica, which limited the potential temperature of application of the composites. Instead, the positive role of the preceramic polymer on the ink rheology was exploited by increasing its concentration in the ink. Rheological characterization carried out on both inks confirmed that they possessed Bingham shear thinning behavior and fast viscosity recovery. Single filaments with different diameters (~310 µm and ~460 µm) were produced with the latter ink by DIW and subsequent pyrolysis. Tested under a four-point flexural test, the filaments showed a mean flexural strength above 30 MPa, graceful failure, and fiber pull-out. The results of this work suggest that CMC components can effectively be fabricated via DIW of a preceramic ink with embedded short fibers; the preceramic polymer is able to provide the desired rheology for the process and to develop a dense matrix capable of incorporating both fibers and ceramic particles, whereas the fibers addition contributes to an increase of the fracture toughness of the material and to the development of a graceful failure mode. View Full-Text
Keywords: CMC; additive manufacturing; preceramic polymers CMC; additive manufacturing; preceramic polymers
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MDPI and ACS Style

Franchin, G.; Maden, H.S.; Wahl, L.; Baliello, A.; Pasetto, M.; Colombo, P. Optimization and Characterization of Preceramic Inks for Direct Ink Writing of Ceramic Matrix Composite Structures. Materials 2018, 11, 515.

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