Direct ink writing of ZrB2-SiC chopped fiber ceramic composites

Ultra-high temperature ceramics (UHTCs) are of interest for thermally- and/or mechanically- extreme environments because of their high melting temperatures (> 3000 degrees C) and ablation resistance. More widespread use is limited by low fracture toughness and inability to be processed into complex-shaped components. Here, we report the production of fiber-reinforced UHTC matrix composites (UHTCMCs) formed via the additive manufacturing technique of direct ink writing (DIW). Slurry 'inks' were developed containing up to 47.5 vol% of the UHTC zirconium diboride (ZrB2), up to 10 vol% chopped silicon carbide fiber (SiCf), and a silicon carbide (SiC) precursor polymer. Lattice structures and flexural specimens were printed and pyrolyzed to form UHTCMCs with aligned (relative to the print direction) SiCf in the ZrB2-SiC matrix. Flexural strength of fiber-containing parts is presented, and fiber alignment due to deposition is analyzed with X-ray computed tomography. Defects that occurred during the DIW process, and their probable causes and mitigation strategies are also discussed.