Free Forming of Porous Ceramic Parts by Rapid Freeze Gelation (RFG)
L. Henkel, Chr. Soltmann, L. Vinke, D. Koch, G. Grathwohl
University of Bremen, Advanced Ceramics Group, Bremen, Germany
received January 24, 2011, received in revised form March 07, 2011, accepted March 19, 2011
Vol.2, No.2, Pages 125-132 DOI: 10.4416/JCST2011-00004
A novel manufacturing route is presented called rapid freeze gelation (RFG) for the fabrication of silica-sol-based ceramic bodies via freeze consolidation without geometric restrictions. The layer-by-layer shaping method permits a constant freeze velocity over the entire consolidation process. Thus, ceramic parts with homogeneous microstructures can be produced and pore structures can be adjusted as intended. The final pore structure is templated by means of ice crystallization, which is controlled by the freezing conditions and the effect of freezing modifiers such as e.g. glycerol. Ceramic lattice structures are generated with a wide range of porosities up to highly porous networks. A crucial criterion for the quality of the freezing green bodies is the interfacial connection of layers. It is shown that slow freezing rates at temperatures slightly below the crystallization temperature of the suspension are favourable to ensure a strong interconnection between adjacent layers.
Freeze gelation, rapid prototyping, porous ceramic
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