3D-printed nanoporous ceramics: Tunable feedstock for direct ink write and projection microstereolithography

Highlights: • A feedstock compatible with direct ink write and projection microstereolithography is developed to produce nanoporous ceramics with 250–500 μm features. • Pore sizes ranging from 0.10–500 μm are achieved through the introduction of designed structural porosity and partial sintering. • Printing by both techniques is enabled by modifying solids loading in the range from 55 to 70 wt% to tailor feedstock viscosity. Porous ceramic materials have a wide range of potential applications for which controlling the structure across multiple length scales is desirable. Additive manufacturing (AM) of porous ceramics is therefore of interest for design flexibility. Here, a ceramic ink compatible with 2 AM techniques, projection microstereolithography (PμSL) and direct ink write (DIW), was formulated and demonstrated printed parts with a range of controllable feature sizes as well as nanoporosity resulting from partial sintering. A diacrylate polymer was mixed with 3% yttria partially stabilized zirconia (3YZ) ceramic nanoparticles having different sizes and solids loadings to find formulations that meet the printing requirements of both AM techniques. Detailed rheological studies were used to determine optimal ink formulations to use for either printing method. The resulting 3YZ structures printed with DIW and PμSL have engineered macro cavities with span lengths greater than several millimeters, wall thicknesses of 200 to 540 μm, and porosity within the wall structure on the order of 100 nm. This study revealed that through facile composition changes to the 3YZ ink, it was feasible to use the same ink base for multiple AM techniques without the need for separate cumbersome ink development processes.