Paste extrusion-based 3D printing of fiber-reinforced ultra high-temperature ceramics

Abstract

Ultra–high-temperature ceramics (UHTCs) are valued for their extremely high melting temperatures and resistance to active oxidation. However, their low fracture strengths and the difficulties in shaping them into complex geometries hamper their widespread application. This study aims to fabricate zirconium diboride–silicon carbide (ZrB₂-SiC) composites reinforced with aligned SiC fibers by formulating suspensions containing a preceramic polymer, ZrB₂, and SiC fibers. This study assessed the influence of fiber alignment on electrical and thermal conductivities, as well as on mechanical strength. The results revealed a significant enhancement in thermal conductivity, particularly when the fibers were aligned, effectively doubling it compared with the non-aligned parts. Additionally, increasing the fiber content significantly improved the fracture strength, with composites containing 22.5 vol% fibers reaching fracture strengths over 57 MPa. However, the final values did not meet the theoretical expectations because the porosity in pyrolyzed parts exceeded 10%. Furthermore, the study demonstrated a 10-fold increase in electrical conductivity with fiber alignment compared to that for non-aligned composites. These results highlight the capability of paste extrusion-based additive manufacturing in tailoring ultra–high-temperature ceramic matrix composites (UHTCMCs) with aligned fibers, realizing their suitability for aerospace applications.