Formation mechanism and controlling strategy of lamellar structure in 3D printed alumina ceramics by digital light processing

Digital light processing has brought great improvements to ceramic material shaping, along with new challenges to the control of material structures and properties. Its layer-by-layer manufacturing pattern always results in a lamellar structure or sintering shrinkage anisotropy. This study introduces a simple strategy for revealing the spatial distribution of the ceramic powders and resin in a printed precursor, by which the formation mechanisms of the lamellar structure during the printing process can be studied. The results show that the sedimentation of the ceramic powders leads to resin enrichment between the layers. After the debinding process, the layers are indirectly connected by discrete ceramic particles, resulting in the lamellar structure. In addition, the evolution of the lamellar structure throughout the entire sintering process and its effects on the sintering shrinkage and strength of the printed ceramics are investigated. The disappearance of the large pores distributed at the layer interfaces during the sintering contributes to the extra shrinkage in the height direction. By combining the experimental data and finite element method, it is revealed that the lamellar structure shows different deformation behaviors under loadings with varying directions, leading to an apparent strength anisotropy. In addition, a design strategy is discussed for the lamellar structure, i.e., for controlling the strength anisotropy and its corresponding application. This study can be of great assistance for the design of structures and strengths in the additive manufacturing of ceramics.