Basar Ozkan, Ayoub Khouyi, Fatih Tarak, Farzaneh Sameni, Leah Okoruwa, Ehsan Sabet
Controlling light absorption in digital light processing (DLP) via pigment incorporation offers a versatile approach to tuning curing dynamics, shrinkage behaviour, and mechanical performance in ceramic additive manufacturing. In this study, black pigment (BP) was systematically introduced into a silica-based photopolymer suspension to modulate optical attenuation and enhance the geometric fidelity, surface quality, and dimensional accuracy of printed parts. An optimal 2 wt% BP formulation reduced peeling forces by ≈40% and eliminated recoating resistance, enabling smoother layer separation and improved print stability. Cure uniformity was enhanced, suppressing overcuring artefacts and sharpening lateral features. The degree of polymer conversion increased from ≈50% (no pigment) to ≈76%, correlating with reduced early-stage mass loss during thermogravimetric analysis, indicating a more complete crosslinked network and reduced low-temperature volatilization. These effects led to significantly improved mechanical performance, with green strength reaching ≈36 MPa and sintered strength ≈12 MPa, alongside minimized shrinkage anisotropy (ΔZ–XY ≈ 0.12%). Microstructural and profilometric analyses confirmed improved microstructural integrity and surface quality, with lateral surface roughness reduced to ≈4 μm and cure-induced overgrowth eliminated. Cure depth tuning effectively confined light penetration, improving interlayer bonding and dimensional precision. A full-scale silica-based ceramic core printed with the optimized formulation preserved intricate features and achieved dimensional accuracy within ±0.5 mm after sintering. These findings demonstrate that, within the studied silica-based system, pigment-modified photopolymer formulations enable high-resolution, low-defect DLP ceramic printing, offering a scalable and reliable route for precision components in aerospace, investment casting, and high-temperature tooling.