The impact of heat treatment on the microstructure of a clay ceramic and its thermal and mechanical properties

Pierre-Marie Nigay (1, 2) , Thierry Cutard (2) , Ange Nzihou (1)

1 RAPSODEE - Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement
2 ICA - Institut Clément Ader

This paper presents the results of an experimental study on the microstructure, the thermal and the mechanical properties of a clay-based ceramic used in building applications. The X-ray tomography analysis showed a layered microstructure of clay with 200 mu m sheets of porosity after the extrusion process. The gas release from the dehydration, dehydroxylation and decarbonation induced a 7 vol% formation of porosity during the heat treatment of the clay-based ceramic up to 850 degrees C. The porosity increase and the development of metakaolin led to a 38% decrease in the thermal conductivity. On the other hand, the Young's modulus of the clay-based ceramic was conserved due to the formation of smaller pores than the 200 mu m sheets of porosity. The densification and the crystallization of amorphous phases also led to a 110% increase of the Young's modulus from 850 degrees C to 1050 degrees C. The Young's modulus of the clay-based ceramic was only decreased by the 13 Kt quartz inversion of the cooling due to sand addition. Hence, this study provided a useful insight into how the microstructure of fired clay bricks can be specifically transformed by the porosity during the heat treatment to control the thermal and mechanical properties.

Mots clés: Young's modulus; Porosity; Thermal conductivity; Clay; Ceramic

Domaines: Sciences de l'ingénieur [physics]

Pierre-Marie Nigay, Thierry Cutard, Ange Nzihou. The impact of heat treatment on the microstructure of a clay ceramic and its thermal and mechanical properties. Ceramics International, 2017, 43 (2), p.1747-1754. ⟨10.1016/j.ceramint.2016.10.084⟩. ⟨hal-01619238⟩