Mechanical reinforcement of 3D-printed polymer-derived ceramics with boron nitride nanotubes

Additive manufacturing (AM), or three-dimensional (3D) printing, has the potential to transform the high-resolution fabrication of polymer-derived ceramics (PDCs) and broaden their applications. However, the inherently porous microstructure of PDCs, often exacerbated by AM, significantly degrades their mechanical performance, posing a major scientific and technological challenge. In this work, we investigate the mechanical reinforcement of 3D-printed PDCs using boron nitride nanotubes (BNNTs). Incorporating a small amount of BNNTs (up to 0.3 wt.%) into polymer-derived silicon oxycarbide (SiOC) fabricated by digital light processing substantially improves bulk mechanical properties. Compared with pure PDC pyrolyzed at 1000 °C, the 0.3 wt.% BNNT-PDC annealed at 1400 °C exhibits approximately 106% higher flexural modulus, 120% higher flexural strength, and 272% higher hardness. The maximum toughness is obtained for the 0.3 wt.% BNNT-PDC pyrolyzed at 1000 °C, representing an approximately 148% improvement over pure PDC processed at the same temperature. These enhancements are attributed to the synergistic effects of direct BNNT reinforcement, nanotube-matrix interactions, BNNT-mediated microstructural evolution, and high-temperature-induced evolution of the ceramic matrix. Collectively, these findings provide new insights into the interplay among processing, microstructure, interfacial interactions, and mechanical performance in BNNT-reinforced PDCs, establishing a foundation for the rational design and AM of next-generation ceramic components with enhanced strength, toughness, and reliability.