Designing curing layer structures to manage the anisotropies of alumina ceramics manufactured by vat photopolymerization

Controlling for anisotropic dimensional shrinkage, three-point bending strength, and fracture toughness are significant scientific issues in the fields of ceramic cores and bioceramics and are primarily influenced by oriented lamellar structures. For this purpose, this work designs some micro-sized hollow rectangular structures to transform lamellar structures into T-shaped dislocation layer structures which improve the section factor, thus controlling the anisotropic properties. Starting from the theoretical equation of curing depth, a novel photopolymerization profile curve equation is established to accurately predict the actual curing profile curve, guiding microstructural design. The photopolymerization state of the green body with a microstructural design is consistent with that of normal printing. This experiment investigates the control benefits of microstructural design parameters (the length, width, and area percentage of the rectangle) and sintering temperature on dimensional shrinkage, bending strength, and fracture toughness. The microstructural design method provides a dimension shrinkage control benefit of −4.02–7.22 % for the x direction, −3.59–9.53 % for the y direction, and −5.54–8.48 % for the z direction, a bending strength enhancement effect of −12.97–25.73 % in the x direction and −17.64–16.88 % in the z direction, and a fracture toughness reinforcement effect of 2.5–36.67 % in the x direction and 6.47–82.86 % in the z direction, which results in a reduction rate of anisotropic dimensional shrinkage and strength ranging from −175.90–32.85 % and 4.34–75.49 %, respectively. The maximum bending strength and fracture toughness reach 331.40 MPa and 6.14 MPa∙m^1/2, respectively. This provides a common control method for the dimension and mechanical properties of any material via VPP additive manufacturing.