Stencil additive manufacturing: An approach to fabricating porous 3D lattice alumina structures

Abstract

This work employed the Stencil Additive Manufacturing (SAM) technique to fabricate α-alumina lattice structures. A ceramic slurry system based on Pluronic F-127 hydrogel was formulated to carry nano-sized α-alumina ceramic particles, achieving a solid loading of 37 vol%. The slurry exhibited non-Newtonian behaviour, making it suitable for stencil printing applications. Rheological characterisation revealed an elastic modulus of 19,600 kPa and a storage modulus of 996 kPa. Flow tests were successfully fitted to the Herschel-Bulkley model, yielding at 213.38 Pa, a flow index of 0.21, and a consistency index of 4259.24 Pa s, confirming the slurry's shear-thinning behaviour, an essential property for SAM. Stencil printing of ceramic hydrogel layers, followed by controlled drying and sintering at 1550 °C, resulted in the successful fabrication of rigid α-alumina ceramic parts. Post-sintering analysis demonstrated that crack-free specimens with heights up to 5.25 mm, maximum warping of 10 %, and 94–98 % density were achieved. The study highlights the potential of SAM for the additive manufacturing of ceramics, presenting a novel approach to fabricating complex ceramic structures. While the process shows promise, limitations such as channel closure during deposition and warping during drying must be addressed to further improve shape fidelity and accuracy. This research opens avenues for the future development of stencil-based additive manufacturing in ceramic production, which shows promise as a viable pathway to the mass manufacturing of parts.