Abstract
With a novel Freeze Foaming method, it is possible to manufacture porous cellular components whose structure and composition also enables them for application as artificial bones, among others. To tune the foam properties to our needs, we have to understand the principles of the foaming process and how the relevant process parameters and the foam’s structure are linked. Using in situ analysis methods, like X-ray microcomputed tomography (µCT), the foam structure and its development can be observed and correlated to its properties. For this purpose, a device was designed at the Institute of Lightweight Engineering and Polymer Technology (ILK). Due to varying suspension temperature and the rate of pressure decrease it was possible to analyze the foam’s developmental stages for the first time. After successfully identifying the mechanism of foam creation and cell structure formation, process routes for tailored foams can be developed in future.
Highlights
The two conventional processes for manufacturing ceramic cellular foam structures are the replica, as well as the space holder method [1,2]
The ceramic suspensions used in this work are composed of water and dispersion agent
The choice of suspension and composition was derived from preliminary tests on the basis of different suspensions which, after Freeze Foaming, resulted in reproducible foam structures [23]
Summary
The two conventional processes for manufacturing ceramic cellular foam structures are the replica, as well as the space holder method [1,2] These methods use organic scaffolds, which have to be burnt out. Since the pressure is reduced further, the temperature falls beneath the equilibrium temperature in the triple point of our suspension, which causes our created structure to be instantly frozen, and dries via sublimation. This freezing step can result in cryogenic structures similar to typical freeze cast structures [5,6] and accounts for the microporosity of foamed structures. Possible applications of foams and porous parts made using Freeze Foaming encompass a Materials 2018, 11, 2478; doi:10.3390/ma11122478 www.mdpi.com/journal/materials
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