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Effects of densification and mullitization on the evolution of the elastic properties of a clay-based material during firing

Authors
Journal
Journal of the European Ceramic Society
0955-2219
Publisher
Elsevier
Publication Date
Volume
29
Issue
9
Identifiers
DOI: 10.1016/j.jeurceramsoc.2008.09.020
Keywords
  • Platelets
  • Non-Destructive Evaluation
  • High Temperature Ultrasonic Echography
  • Inclusions
  • Microstructure-Final
  • Clay

Abstract

Abstract The microstructural evolution of an illito-kaolinitic raw material has been characterized during firing at 10 °C/min up to 1200 °C. The strong evolution of porosity and amount of mullite formed from the viscous flux (from 1000 °C) has been quantified using dilatometric measurement, image analysis and X-ray diffraction. In situ ultrasonic echography has been used in order to determine the Young's modulus ( E) evolution associated to the microstructural changes. This technique is highly sensitive to porosity elimination and mullite development even though an abundant viscous flux is present. For low amount of mullite (<24.7 vol.%), the E evolution observed can be easily related to porosity and mullite volume proportion changes by applying the Hashin & Shtrikman approach (lower bound). For higher mullite content, the strong experimental E increase observed between 25.9 and 51.2 GPa has been related to the transition from isolated rigid inclusions (mullite and quartz) in soft matrix (viscous flux) toward a percolating network.

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