Flexible and Tough Nanofibrous Ceramics via the Additive Manufacturing of Self-Assembling Preceramic Polymer-Block Copolymer Feedstocks

Ceramic nanofiber architectures are useful for a wide range of applications, including lightweight structures, filtration, and catalyst supports, due to their high specific surface area, chemical resistance, and thermal stability. To date, ceramic nanofibers have been predominately fabricated by electrospinning; however, controlling nanofiber alignment within complex architectures is not possible by this technique. Here, we report the in-situ generation of aligned ceramic nanofibers that form through a combination of polymer self-assembly and additive manufacturing. Specifically, preceramic polymer and block copolymer feedstock blends were observed to phase separate during the heat treatment of printed filaments. Nanofiber alignment appears to be influenced by confinement effects imposed on the self-assembling polymers by the printed filament geometry. Following curing, the printed structures were pyrolyzed to generate complex objects composed of ceramic nanofibers. As exemplars, we have printed one-dimensional nanofibrous tows, springs, and lattices that can be manipulated by bending and twisting without mechanical failure. Tensile testing of filaments composed of self-assembled ceramic nanofibers revealed substantial nanofiber pullout, which is attractive for future applications in composites. A spring made from nanofiber-containing filament could be compressed and strained by 50% with only minor hysteresis in the force required to strain the spring. The facile, integrated approach of combining molecular self-assembly with additive manufacturing opens new avenues for producing ceramic nanofiber-based architectures and composites for use in elevated temperature applications (e.g., aerospace, filtration, and catalysts supports).