On the stress-free lattice expansion of porous cordierite / Giovanni Bruno in Acta materialia, Vol. 58 N° 6 (Avril 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 6 (Avril 2010) . - pp. 1994–2003 Titre : On the stress-free lattice expansion of porous cordierite Type de document : texte imprimé Auteurs : Giovanni Bruno, Auteur ; Alexander M. Efremov, Auteur ; Bjørn Clausen, Auteur Année de publication : 2011 Article en page(s) : pp. 1994–2003 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Micro-strains Neutron diffraction Thermal expansion Integrity factor Micro-cracking Résumé : An extensive investigation of the lattice expansion (up to 1200 °C) of porous synthetic cordierite (obtained by firing a mixture of talc, clay, alumina and silica) was carried out using time-of-flight neutron diffraction at LANSCE, Los Alamos, NM, USA and FNLP, Dubna, Russia. An extruded rod and several powders, with different particle size (dispersity), were studied, with the aim of monitoring the variation of the (lattice) micro-strain as a function of temperature and its influence on the microscopic and macroscopic thermal expansion. Results show a different expansion of the a- and b-axes of the orthorhombic cell (in the rod above 800 °C). While the finest powder seems to contract more along the c-axis, thus hinting at the presence of smaller stress, the integral peak width increases as a function of temperature in the intermediate range (300–700 °C). This could be explained by the integrity factor modeling in terms of micro-cracking. In polycrystalline cordierite, the model implies tension along the a- and b-axes (positive thermal expansion) accompanied by compression along the c-axis (negative thermal expansion) and a stress release upon cooling, via a thermal micro-cracking mechanism. The calculations of the cordierite macroscopic thermal expansion having as input crystal axial expansions assumed to be stress-free allowed us to conclude that even a fine powder (5 μm particle size) cannot be considered completely stress-free. This conclusion is supported by microstructural observations. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008210 [article] On the stress-free lattice expansion of porous cordierite [texte imprimé] / Giovanni Bruno, Auteur ; Alexander M. Efremov, Auteur ; Bjørn Clausen, Auteur . - 2011 . - pp. 1994–2003. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 6 (Avril 2010) . - pp. 1994–2003 Mots-clés : Micro-strains Neutron diffraction Thermal expansion Integrity factor Micro-cracking Résumé : An extensive investigation of the lattice expansion (up to 1200 °C) of porous synthetic cordierite (obtained by firing a mixture of talc, clay, alumina and silica) was carried out using time-of-flight neutron diffraction at LANSCE, Los Alamos, NM, USA and FNLP, Dubna, Russia. An extruded rod and several powders, with different particle size (dispersity), were studied, with the aim of monitoring the variation of the (lattice) micro-strain as a function of temperature and its influence on the microscopic and macroscopic thermal expansion. Results show a different expansion of the a- and b-axes of the orthorhombic cell (in the rod above 800 °C). While the finest powder seems to contract more along the c-axis, thus hinting at the presence of smaller stress, the integral peak width increases as a function of temperature in the intermediate range (300–700 °C). This could be explained by the integrity factor modeling in terms of micro-cracking. In polycrystalline cordierite, the model implies tension along the a- and b-axes (positive thermal expansion) accompanied by compression along the c-axis (negative thermal expansion) and a stress release upon cooling, via a thermal micro-cracking mechanism. The calculations of the cordierite macroscopic thermal expansion having as input crystal axial expansions assumed to be stress-free allowed us to conclude that even a fine powder (5 μm particle size) cannot be considered completely stress-free. This conclusion is supported by microstructural observations. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008210

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