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Sintering and shrinkage behavior of complex cellular ceramic structuresThursday (08.10.2020) 11:50 - 12:10
One of the crucial steps in the processing of ceramic materials is sintering at elevated temperature. During this process, the ceramic part adopts its final shape and develops its desired properties. Depending on the ceramic material, a more or less significant (volumetric) shrinkage from the green body dimensions to the finally sintered geometry is obtained, and this holds, too, for cellular ceramic materials
However, the structural complexity of ceramic foams is much higher compared to bulk ceramic parts. This manifests in the presence of various structural features, for example the foam struts and the strut nodes, which enclose a complex pore network being comprised of foam cells, hollow strut cavities and strut material pores.
The characterization of the shrinkage behavior of cellular ceramics is usually limited to the examination of the geometrical foam dimensions, from which an average linear and volumetric shrinkage is estimated. Although the overall dimension of ceramic foams decreases during sintering, the evolution of other structural features, for example the cell size and the dimension of the hollow strut cavities remains unclear. As the shrinkage is a consequence of material rearrangement in the solid part of the foam structure, deviations between the strut diameter evolution, for example, and the course of the cell size during sintering is expected.
In the present study, alumina foams were manufactured by the sponge replication (Schwartzwalder) technique and sintered at temperatures between 1250 °C and 1650 °C. The foams were characterized regarding their porosity and shrinkage behavior by micro computed tomography, mercury intrusion porometry and conventional pore analysis based on the Archimedes principle. From these data, the shrinkage behavior and the evolution of specific structural parameters, e. g. cell size, strut diameter and hollow strut diameter, was derived and correlated, among others, with the sintering temperature. In conclusion, this leads to a deeper insight into the sintering and shrinkage behavior of cellular ceramic structures.