Freeze-casting: Fabrication of highly porous and hierarchical ceramic supports for energy applications

Abstract

[EN] The manufacture of structured ceramic porous support knows an important boom since more than a decade with the development of new shaping techniques. Among the most promising ones, the freeze-casting also called Ice-Templating allows the fabrication of ceramic parts exhibiting high porosity (>50%) and vertically aligned and hierarchically organized pores. Such structures were firstly conceived for biomedical applications like bone substitute and tissue engineering, but the distinctive features of freeze-cast structures have attracted the attention of diverse scientific fields, especially in high temperature ceramic based energy production systems. Indeed, technologies like (a) Solid Oxide Fuel Cell (SOFC) and Electrolyser Cell (SOEC), (b) gas separation (O-2, H-2) by asymmetric supported membranes based on mixed ionic and electronic conductors (MIEC) or hydrogen-permeable metals, and (c) Catalytic Membrane Reactor (CMR) systems present a porous component in their physical structure. This latest, presenting a tortuous pathway for gas access and as a consequence, a high transport limitation, is known to be a limiting component for the operation at high flow streams that would enable to reach industrial target.

The aim of this paper is to give an overview of the freeze-casting ceramic shaping method and to show how its implementation could be useful for several energy applications where key components comprise a porous scaffold. A detailed presentation of the freeze-casting process and of the characteristics of the resulting porous parts is firstly given. The characteristic of freeze-cast parts and the drawbacks of conventional porous scaffolds existing in energy applications are drawn in order to highlight the expected beneficial effect of this new shaping technique as possible substitute to the conventional ones. Finally, a review of the state of the art freeze-cast based energy applications developed up to now and expected to be promising is given to illustrate the large perspectives opened by the implementation of the freeze-casting of ceramics for energy fields. Here we suggest discussing about the feasibility of incorporate freeze-cast porous support in high temperature ceramic-based energy applications. (C) 2016 SECV. Published by Elsevier Espana, S.L.U.

[ES] La fabricación de soportes cerámicos porosos a través de nuevas técnicas de conformado es clave en el desarrollo de nuevos dispositivos en el sector energético y de la ingeniería química. La técnica de freeze-casting (colado por congelación) permite obtener componentes cerámicos muy bien sinterizados, con muy alta porosidad y poros con formas concretas. Los poros se orientan de manera que las propiedades de transporte de fluidos a su través son óptimos con respecto a otros tipos de estructuras porosas más irregulares. Concretamente, en el sector de la energía los soportes porosos se utilizan en aplicaciones tales como pilas de combustibles de óxidos sólidos o electrolizadores, membranas para la separación de gases, típicamente O2 o H2, y reactores catalíticos de membrana. En este artículo se revisan de manera exhaustiva los desarrollos en estos campos utilizando freeze-casting para el conformado de cuerpos porosos cerámicos. © 2016 SECV. Publicado por Elsevier España, S.L.U