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Robocasting of Alumina Lattice Truss Structures
T. Schlordt, F. Keppner, N. Travitzky, P. Greil
Department of Materials Science, Glass and Ceramics, Friedrich-Alexander-University Erlangen-Nuernberg, Martensstr. 5, 91058 Erlangen, Germany
received January 20, 2012, received in revised form February 8, 2012, accepted February 25, 2012
Vol. 3, No. 2, Pages 81-88 DOI: 10.4416/JCST2012-00003
Abstract
Robocasting of aqueous colloidal α-Al2O3 gels for manufacturing cellular ceramics with periodical lattice truss structures was investigated. Coagulation of gels loaded with 48 vol% α-Al2O3 was induced by adding CH3COONH4. The gels exhibit shear-thinning behavior, shear elastic moduli ranging from 6.7 to 390 kPa and yield-stresses from 25 to 570 Pa. Continuous filaments with a diameter of 0.5 mm were extruded with a deposition speed of up to 35 mm/s on a high-precision six-axis robotic system equipped with a single-screw micro-extruder. The lattice structures consist of alternating layers formed by a linear array of circular rods aligned parallel with a distance of 1 mm and an angle of 90° between alternating layers. After being dried for 12 h, the robocast grids were sintered in air at 1650 °C for 2 h resulting in a fractional strut density > 0.95, a mean filament diameter of 400 μm, a volume filling fraction of 0.49 (sealed walls) and 0.35 (meshed walls), and macro-cells in the deposition plane of quadratic shape with a mean area of 0.136 mm2 ± 0.017 mm2 Based on gravitation-driven viscous flow, model conditions for attaining free spanning ligaments were discussed.
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Keywords
Robocasting, alumina gel, lattice truss structures
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