Engineering applications of ceramic foams

Engineering applications of ceramic foams Nature offers several examples of cellular materials, such as cork and sponges that man has been using for thousands of years; only recently, he started producing artificial materials mimicking these structures. This approach allowed to extend the range of materials’ physical properties, allowing engineering solutions unfeasible with dense matter. In the last decade, there has been an increasing interest in the development of highly porous ceramic materials. In fact, these materials show the unique capability of conjugating properties of ceramics (high temperature resistance, chemical inertia) to properties typical of their cellular structure (low density, high permeability, thermal shock resistance). The aim of this PhD work is to explore ceramic foams for two different engineering fields: energy conversion systems and biomaterials. A method for the preparation of ceramic foams was developed, involving the preparation of a ceramic powder loaded polyurethane foam. For energy applications, the technique was used to produce porous anode layers for intermediate temperature solid oxide fuel cells. Cermet nickel/yttria-stabilized zirconia foams with hierarchical porosity were prepared following different processing routes and characterized in terms of morphology, porosity and electrical conductivity. In the application for biomaterials, the foaming technique was used for the preparation of bioactive glassceramics shaped accordingly to a patient specific geometry. This involved the segmentation of a three dimensional model of a bone portion, reconstructed from computer axial tomography data. Foam materials in the SiO2-CaO-P2O5 were prepared and characterized in terms of morphology and cristallinity. Bioactivity was assessed in vitro, confirming the formation of a bone-like hydroxylapatite layer on the surface of the material. Both applications showed the great potential of the in situ foaming technique for the preparation of cellular ceramics with tailored porosity.