Lightweight and stiff cellular ceramic structures by ice templating
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ric Maire Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, Villeurbanne, France
Sylvain Deville Laboratoire de Synthèse et Fonctionnalisation des Céramiques, UMR3080 CNRS/Saint-Gobain, Cavaillon, France (Received 4 September 2013; accepted 25 November 2013)
Porous, strong, and stiff ceramic materials are required for a range of technical applications, involving for instance, liquid or gas flow. Natural materials such as wood can provide useful structural guidelines for the optimal microstructural design, although only few processing routes are able to turn these guidelines into actual materials. We illustrate here, how ice templating of anisotropic particle suspensions can be modified to obtain a honeycomb structure with pores of 30 lm diameter. The growth of ice crystals in the slurry induces self-assembly of the anisotropic particles, leading to relatively thin walls (10 lm). Because large anisotropic particles are difficult to sinter, a glassy phase was introduced to facilitate this densification step and then to further reduce the walls’ porosity. Young’s modulus and compressive strength were both improved by the addition of a glassy phase by an order of magnitude due to the denser walls. These macroporous materials are more robust and stiff than materials with an equivalent morphology, while offering a simple alternative to the current wood replica processing routes.
I. INTRODUCTION
The mechanical properties of porous cellular materials directly depend on their cell structure. Natural materials such as wood, because their role is to withstand stress and to mediate water and nutriments transfer, provide guidelines to obtain cellular materials with remarkable stiffness and tailored porosity. The most common cellular structure encountered in a load-bearing natural material is the honeycomb because this geometry provides a very high specific elastic modulus.1 The pores need to be as parallel and straight as possible while the hexagonal shape maximizes the structural stiffness. The options to obtain cellular ceramic materials with an oriented anisotropic porosity are limited when the targeted cell size and cell wall thickness are similar to that of wood (typically 30 lm cell size and less than 5 lm in wall thickness for balsa2). Wood structures are defined by a delicate balance between the densities of pores (to have a large accessible area), large and straight pores to limit the pressure drop, and cell structure and wall thickness to provide structural resistance. Cellular ceramics presenting such characteristics can be useful as supports for a liquid or gaseous chemical reaction and, more generally, as a fluid carrier. Usual ceramic foams partly fulfill those a)
Address all correspondence to this author. e-mail: fl[email protected] DOI: 10.1557/jmr.2013.385 J. Mater. Res., Vol. 29, No. 2, Jan 28, 2014
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requirements, such as a high porosity content and high strength, but their low cell connectivity and high tortuosity may restrain their use for tho
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