Process Development For HIAM Of Ceria-Stabilized Zirconia: Linking Hydrogel Network Characteristics To Ce/Zr Infusion And 3d Lattice Fabrication

Abstract

Hydrogel-infusion additive manufacturing (HIAM) is a vat photopolymerization-based technique that decouples geometry definition from material selection, using a particle-free hydrogel scaffold as a structural template into which material identity is introduced through post-print infusion of aqueous metal salt precursors. This thesis investigates the application of HIAM to the fabrication of ceria-stabilized zirconia (CSZ) ceramic lattices and establishes the link between hydrogel network characteristics, Ce/Zr infusion behavior, and 3D lattice fabricability. This material system presents distinct challenges relative to prior HIAM demonstrations due to the limited aqueous solubility of zirconium precursors and the differential interaction of Ce³⁺ and Zr⁴⁺ with the polymer network.A 3×3 factorial parametric study varying PEGDA/PEGMA molar ratio (100/0, 75/25, 50/50) and polymer-to-water weight fraction (30/70, 50/50, 70/30) across three UV exposure durations (10, 15, 20 s) identified the network formulation that maximizes equilibrium water content (EWC). The highest EWC of 71.70% was achieved with 50/50 PEGDA/PEGMA, 30/70 polymer/water at 10 s UV exposure (Vial 7), representing an improved composition for ion infusion. However, Vial 7 could not be reliably printed on the Phrozen Sonic Mini 8K due to its high water content, and the next-best formulation (Vial 8: 50/50 PEGDA/PEGMA, 50/50 polymer/water, 10 s UV) was adopted as the working formulation for all subsequent printing and infusion work. Infusion experiments with 2 M CeCl₃·7H₂O and 2 M ZrOCl₂·8H₂O solutions revealed an asymmetry in ion uptake. Ce³⁺-infused discs achieved a net overnight mass gain of approximately 11.4% above the swollen baseline, while Zr⁴⁺-infused discs reached only approximately 6.7%, consistent with the higher charge density and reduced mobility of Zr⁴⁺ within the polymer network. Elevated-temperature infusion at 60 °C accelerated kinetics but introduced concave warping incompatible with geometric fidelity, identifying room-temperature overnight infusion at 2 M as the most suitable condition. Preliminary precipitation trials using ammonium hydroxide solution were unsuccessful, as the precipitating agent displaced previously absorbed ions rather than fixing them within the network. Gyroid lattice structures were printed using the Vial 8 formulation and advanced to the precipitation stage, with two surviving structures obtained from approximately 24 attempts due to build plate adhesion failures and the geometric demands of the gyroid architecture. The results establish an initial process window for CSZ HIAM and identify three technical barriers that must be addressed to advance the material system toward functional ceramic fabrication: precursor loading, precipitation chemistry, and print process reliability.