Robocasting of carbon-alumina core-shell composites using co-extrusion
Abstract
Purpose
This study aims to achieve the fabrication of three-dimensional core-shell filament-based lattice structures by means of robocasting combined with co-extrusion. For core and shell materials, colloidal gels composed of submicron carbon and alumina powders were developed, respectively. Simultaneously, the co-extrusion process was also studied by numerical simulation to investigate the feed pressure-dependent wall thickness.
Design/methodology/approach
Significant differences in the rheological behavior of the carbon and alumina gels were observed because of differences of the particle morphology and surface chemistry of the carbon and alumina powders. Precise control over the cross-sectional diameter of the core and shell green state elements was achieved by alteration of the feed pressures used during co-extrusion.
Findings
After subsequent thermal treatment in an oxidizing atmosphere (e.g. air), in which the carbon core was oxidized and burned out, lattice structures formed of hollow filaments of predetermined wall thickness were manufactured; additionally, C-Al2O3 core-shell filament lattice structures could be derived after firing in an argon atmosphere.
Originality/value
Green lattice truss structures with carbon core and alumina shell filaments were successfully manufactured by robotically controlled co-extrusion. As feedstocks carbon and alumina gels with significantly different rheological properties were prepared. During co-extrusion, the core paste exhibited a much higher viscosity than the shell paste, which benefited the co-extrusion process. Simultaneously, the core and shell diameters were exactly controlled by core and shell feed pressures and studied by numerical simulation. The experimentally and numerically derived filament wall thickness showed qualitative agreement with each other; with decreasing core pressure during co-extrusion, the wall thickness increased.
Keywords
Acknowledgements
The authors would like to acknowledge the financial support from the Deutsche Forschungsgemeinschaft (DFG TR 250/6-1) and the Exzellenzcluster “Engineering of Advanced Materials”. Furthermore, they wish to thank Mrs Rong Zhao and Dr Joseph Harris from the University of Erlangen-Nuremberg for Helpful comments.
Citation
Fu, Z., Freihart, M., Schlordt, T., Fey, T., Kraft, T., Greil, P. and Travitzky, N. (2017), "Robocasting of carbon-alumina core-shell composites using co-extrusion", Rapid Prototyping Journal, Vol. 23 No. 2, pp. 423-433. https://doi.org/10.1108/RPJ-12-2015-0191
Publisher
:Emerald Publishing Limited
Copyright © 2017, Emerald Publishing Limited