Alumina Porous Ceramics Obtained by Freeze Casting: Structure and Mechanical Behaviour under Compression

• Published in: Ceramics Vol. 1; no. 1; pp. 83 - 97
• Main Authors: Hautcoeur, Dominique, Gonon, Maurice, Baudin, Carmen, Lardot, Véronique, Leriche, Anne, Cambier, Francis
• Format: Journal Article
• Language: English
• Published: MDPI 01.09.2018
• Subjects: Chemical Sciences; Engineering Sciences; Life Sciences; ice templating; freeze casting; strain mode; mechanical properties; porosity gradient effect
• ISSN: 2571-6131; 2571-6131
• DOI: 10.3390/ceramics1010008

The aim of the work is to analyse the mechanical behaviour of anisotropic porous alumina ceramics processed by freeze casting (ice templating). The freeze cast specimens were characterised by a lamellar structure with ellipsoidal pore shape, with a size ranging from 6 to 42 µm and 13 to 300 µm for the minor and major axes, respectively, as a function of the freezing rate and the powder and binder contents. The pore volume fraction ranged from 40 to 57%. SEM analysis of the porous structures after the compression test showed a typical deformation pattern caused by the porosity gradient through the specimen, as determined by X-ray radiography. The apparent elastic modulus of the anisotropic porous alumina ranged from 0.2 to 14 GPa and the compressive strength from 6 to 111 MPa, varying as a function of the process parameters which determine the pore network characteristics. The relationships between stress-strain behaviour in compression and the microstructure and texture were established. An analytical model based on a Gibson and Ashby relationship was used and adapted from SEM microstructural analysis after a mechanical test in order to predict the compressive strength of processed anisotropic alumina.