Novel ink formulation to enable rapid debinding and sintering of alumina fabricated via vat photopolymerization

Vat photopolymerization is an additive manufacturing technology that allows the fabrication of complex ceramic structures with very high resolution, in the order of 10 – 100 µm. However, the bottle neck of the whole production process is represented by the delicate thermal debinding and sintering profiles required to obtain a dense and defect-free ceramics. Herein, this work focuses on developing a novel ink formulation to produce dense alumina (Al2O3) parts with minimal defects. The goal was to obtain the highest possible solid loading while ensuring that the ink exhibited suitable rheological properties for the VP process. Camphor was used as a diluent to reduce the viscosity of the ink and facilitate both the printing and the debinding process. Several inks with varying Al2O3 content were prepared and characterized in detail to investigate their ability to produce defect-free components, with a particular focus on rheological behavior. The printed samples were first cleaned in water, then post cured, debinded (1 – 2 °C/min) in argon and finally sintered in 60 s – 600 s using ultra-fast high temperature sintering (UHS), achieving a sintering time reduction of almost 99% compared to conventional sintering. The samples were sintered to very high relative density (up to 98%) without any noticeable defects. This approach of shaping and sintering complex ceramic objects in few seconds has the potential to provide an energy-efficient alternative to conventional techniques such as pressureless sintering, hence representing a small step in the direction of addressing the current energy crisis.