Additive Manufacturing of Ceramics from Liquid Feedstocks

In this review, we summarize the research activities carried out by our research group at the University of Padova on the additive manufacturing of ceramics from liquid feedstocks. Particularly, we evaluate the use of preceramic polymers, geopolymers, and sol-gel solutions. We mainly focus on processing with liquid feedstocks because they have some advantages with respect to slurry-based feedstocks in which powders are present. Particularly, lower viscosity, enhanced transparency, and lack of scattering and sedimentation are advantageous features for vat photopolymerization processes, whereas the absence of particulates reduces clogging problems at the nozzle for extrusion-based processes. Simultaneously, preceramic polymers and geopolymers have some limitations in terms of the range of ceramic compositions that can be obtained; sol-gel solutions are intrinsically unstable, whereas printed objects suffer from drying issues. Nevertheless, we successfully produced high-quality parts using a variety of additive manufacturing techniques, some of which (e.g., volumetric additive manufacturing) have been proposed for the fabrication of ceramic components for the first time.