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Manufacturing of Open-Cell Aluminium Foams: Comparing the Sponge Replication Technique and Its Combination with the Freezing Method. MATERIALS 2022; 15:ma15062147. [PMID: 35329599 PMCID: PMC8953120 DOI: 10.3390/ma15062147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/10/2022] [Accepted: 03/11/2022] [Indexed: 12/04/2022]
Abstract
The manufacturing of aluminium foams with a total porosity of 87% using the sponge replication method and a combination of the sponge replication and freezing technique is presented. Foams with different cell counts were prepared from polyurethane (PU) templates with a pore count per inch (ppi) of 10, 20 and 30; consolidation of the foams was performed in an argon atmosphere at 650 °C. The additional freezing steps resulted in lamellar pores in the foam struts. The formation of lamellar pores increased the specific surface area by a factor of 1.9 compared to foams prepared by the sponge replication method without freezing steps. The formation of additional lamellar pores improved the mechanical properties but reduced the thermal conductivity of the foams. Varying the pore cell sizes of the PU template showed that—compared to foams with dense struts—the highest increase (~7 times) in the specific surface area was observed in foams made from 10 ppi PU templates. The effect of the cell size on the mechanical and thermal properties of aluminium foams was also investigated.
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Werner D, Maier J, Kaube N, Geske V, Behnisch T, Ahlhelm M, Moritz T, Michaelis A, Gude M. Tailoring of Hierarchical Porous Freeze Foam Structures. MATERIALS 2022; 15:ma15030836. [PMID: 35160783 PMCID: PMC8836913 DOI: 10.3390/ma15030836] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/06/2022] [Accepted: 01/19/2022] [Indexed: 12/10/2022]
Abstract
Freeze foaming is a method to manufacture cellular ceramic scaffolds with a hierarchical porous structure. These so-called freeze foams are predestined for the use as bone replacement material because of their internal bone-like structure and biocompatibility. On the one hand, they consist of macrostructural foam cells which are formed by the expansion of gas inside the starting suspension. On the other hand, a porous microstructure inside the foam struts is formed during freezing and subsequent freeze drying of the foamed suspension. The aim of this work is to investigate for the first time the formation of macrostructure and microstructure separately depending on the composition of the suspension and the pressure reduction rate, by means of appropriate characterization methods for the different pore size ranges. Moreover, the foaming behavior itself was characterized by in-situ radiographical and computed tomography (CT) evaluation. As a result, it could be shown that it is possible to tune the macro- and microstructure separately with porosities of 49–74% related to the foam cells and 10–37% inside the struts.
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Affiliation(s)
- David Werner
- Fraunhofer Institute for Ceramic Technologies and Systems, IKTS, Winterbergstraße 28, 01277 Dresden, Germany; (T.M.); (A.M.)
- Correspondence: (D.W.); (J.M.)
| | - Johanna Maier
- Institute of Lightweight Engineering and Polymer Technology, University of Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (V.G.); (T.B.); (M.G.)
- Correspondence: (D.W.); (J.M.)
| | - Nils Kaube
- Fraunhofer Institute for Ceramic Technologies and Systems, IKTS, Maria-Reiche-Str. 2, 01109 Dresden, Germany; (N.K.); (M.A.)
| | - Vinzenz Geske
- Institute of Lightweight Engineering and Polymer Technology, University of Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (V.G.); (T.B.); (M.G.)
| | - Thomas Behnisch
- Institute of Lightweight Engineering and Polymer Technology, University of Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (V.G.); (T.B.); (M.G.)
| | - Matthias Ahlhelm
- Fraunhofer Institute for Ceramic Technologies and Systems, IKTS, Maria-Reiche-Str. 2, 01109 Dresden, Germany; (N.K.); (M.A.)
| | - Tassilo Moritz
- Fraunhofer Institute for Ceramic Technologies and Systems, IKTS, Winterbergstraße 28, 01277 Dresden, Germany; (T.M.); (A.M.)
| | - Alexander Michaelis
- Fraunhofer Institute for Ceramic Technologies and Systems, IKTS, Winterbergstraße 28, 01277 Dresden, Germany; (T.M.); (A.M.)
| | - Maik Gude
- Institute of Lightweight Engineering and Polymer Technology, University of Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (V.G.); (T.B.); (M.G.)
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