Material extrusion for ceramic additive manufacturing with polymer-free ceramic precursor binder

Abstract

Additive manufacturing of dense ceramic products has been challenging because of the high polymeric content of the ceramic feedstock materials. Several studies have been conducted to increase the ceramic content in the feedstock, but the binder and additives in it have remained in the polymeric content. A novel strategy for highly dense additive manufacturing using a sol-gel-based ceramic slurry without polymeric additives is presented. Alumina, which is the most widely used fine ceramic, was chosen as a representative ceramic material. The proposed sol-gel solution enabled a high solid loading of approximately 50 vol% without any polymeric dispersant while satisfying the requirements for material extrusion process, such as extrudable viscosity (<100 Pa.s) and self-sustainable yield stress. This novel sol-gel binder system evolves into aluminum oxide nanoparticles during the sintering process, eventually fusing to the alumina particles. The as-printed green body possessed high alumina content and 66% of theoretical density, which was higher than that obtained via the conventional molding methods. A reduced linear shrinkage of less than 16% and a high density of 99.5% of the theoretical value were also achieved. This research would present a practical strategy for ceramic additive manufacturing as an emerging fabrication process.