Thermomechanical Characterisation of Mullite Zirconia Composites Sintered from Andalusite for High Temperature Applications

Thierry Chotard,Marie-Laure Bouchetou,Lizeth Arbelaez Morales,Jacques Poirier

doi:10.3390/ceramics2040046

Abstract

Mullite-Zirconia refractories are well known for their good resistance to corrosion and thermal shock. In this study, several mullite-zirconia composites were developed from andalusite, alumina and zircon sintered at 1600 °C for 10 hours. The samples were subjected to thermal shock carried out after heating at 1200 °C, in order to study the mechanical and thermomechanical behaviour as a function of the amount of zirconia dispersed in the mullite matrix. It appears that that the amorphous phase (SiO2), determined by X-ray diffraction, produced by the decomposition of andalusite, increases considerably with the amount of final zirconia in the composite and has a very important influence on the porosity. This amorphous phase seems also to have an important influence on the mechanical properties of the material. The characterisation of the thermomechanical behaviour (elastic properties and damage monitoring) was carried out thanks to ultrasonic techniques (US echography and Acoustic Emission). The “surprising” evolution (increase) of the Young’s modulus E of the material after being submitted to repeated thermal shocks is highlighted and explained. The acoustic emission technique carried out at high temperature and also coupled to 4-points bending tests (at room temperature) demonstrates its effectiveness for providing a better understanding of the chronology of the involved mechanisms involved at microstructural scale.

Highlights

Mullite-zirconia refractories are frequently used in the steel and glass industry due to their excellent properties
The classic way to make mullite zirconia composites is by electrofusion of alumina with zircon, which is carried out at a very high temperature due to the high thermodynamic stability of the zircon
For M2 and M3 composite samples, either before and after thermal shocks (Figure 12c–f;), and contrary to the M1(mullite) sample, there is no significant Acoustic Emission (AE) during heating in any thermal cycle

Summary

Introduction

Mullite-zirconia refractories are frequently used in the steel and glass industry due to their excellent properties. The classic way to make mullite zirconia composites is by electrofusion of alumina with zircon, which is carried out at a very high temperature due to the high thermodynamic stability of the zircon The yields of these refractories manufactured by electrofusion are not satisfactory especially in terms of effective lifetime, to replace the use of chromium oxide and alumina-based refractories that give rise to serious environmental problems [9]. Emission method is a non-destructive technique (NDT) which provides useful information on changes and microstructural evolutions induced by different types of solicitations, e.g., solicitations, e.g., mechanical, etc.implemented. It is a part of the implemented industrial. The principle of the AE technique is principle the AE technique onenergy the phenomenon of aform sudden energy release in the material form of based onof the phenomenon ofisa based sudden release in the of acoustic waves when acoustic waves when material undergoes changes in itssignals structure or microstructure

Objectives

Methods

Results

Conclusion