Optimization of the sintering thermal treatment and the ceramic ink used in direct ink writing of α-Al2O3: Characterization and catalytic application

Unlike other engineered ceramic products, alumina (Al2O3) displays interesting mechanical and physical properties, which makes it an ideal candidate for a wide range of uses in different fields and in particular for catalytic applications. However, the manufacturing of ceramic components has still a major drawback in production of highly complex three-dimensional (3D) shapes, microfeatures or structures with tailored porosity. Direct Ink Writing (DIW), also known as robocasting, is a material extrusion Additive Manufacturing technology and is one of such versatile methods with unique flexibility in material and geometry. In this work, alpha-Al2O3 ceramic materials were designed and produced by DIW to determine the most suitable sintering treatment and ceramic ink composition to design new components for catalytic applications. Several thermal treatments varying sintering temperature and time were tested previously to the preparation of inks with different ceramic loadings, up to 75 wt%. A systematic study of the DIW specimens sintered at the optimal sintering temperature - time combination, in terms of microstructure (density and porosity) and mechanical properties (hardness and indentation fracture toughness), was performed to determine the optimize ceramic loading. Finally, finite element modeling and catalytic experiments conducted for the optimal ceramic ink showed that 3D printed parts with a rectilinear infill pattern and 40% infill density favored catalytic performance.