Direct Ink Writing of Binder-Free TiO2 Ceramics: From Paste Engineering to Functional Performance

Abstract

The current study illustrates a binder-free TiO₂ paste, developed using terpineol, a biomass-based solvent, for direct ink writing of 3D structures. It enables the complete elimination of the debinding step. Rheological characterization showed that the formulation P2 (26.77 wt% solid loading) was the most promising with the best printing ability and 30 days of storage stability without any sedimentation or phase separation. At a sintering temperature of 1350 °C, isotropic shrinkage is observed. The isotropic shrinkage characteristics during sintering enable the production of ceramic parts with less than the minimum printing resolution, enabling applications in biomedical, aerospace, automotive, and energy sectors. Sintered samples at optimized temperature obtained strengths of ∼64 MPa and were able to degrade the methylene blue dye by nearly 90% in 7 h. This binder-free approach is simple and energy-efficient for producing high-performance TiO₂ 3D structures.