Optimization, formation, and evolution of the photoinduced curing gradients and in-situ lamellar gaps in additive manufacturing of ZrO2 ceramics: From curing to sintering behaviors

The photoinduced curing gradients and in-situ lamellar gaps were related to the three-dimensional curing mechanism of stereolithography and researched in this work. Based on the photocuring mathematic theories presented by our team, photoinduced curing gradients were influenced by printing parameters such as laser power and frequency, scanning angle, and printing thickness. Among these curing gradients, the inadequate curing area was the main factor affecting the surface quality and physical properties of ceramics. The in-situ lamellar gaps were derived from the inadequate curing area. The lamellar gap size of green bodies was enlarged in brown bodies (sintering at 1170 ℃) and shrunk in sintered bodies (sintering at 1500 ℃). The correlations between the surface quality and printing parameters were clarified by establishing mathematical formulations of the lamellar gap size. Furthermore, anisotropic volume shrinkage, anisotropic surface topography, and density and hardness evolutions were associated with the wrapped particle density differences induced by the photoinduced curing gradients. Finally, the optimal printing parameters (75% of laser power, laser frequency of 150 kHz, scanning angle of 90º, printing thickness of 25 µm, and scanning speed of 2.5 m/s) were obtained by the orthogonal experimental analysis. This study provides a distinct understanding of the high-quality forming and extreme-performance manufacturing of stereolithography.