Paper number 503

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A NANOCOMPOSITE OXIDE SYSTEM : THE NEXTEL 720 FIBRE.

F. Deléglise, M.H. Berger, A.R. Bunsell.

Ecole des Mines de Paris, Centre des Matériaux, BP 87, Evry Cedex, France

Summary

The two phase microstructure and the mechanical properties of the 3M Nextel 720 fibre annealed at different temperatures were investigated. The as received fibre was found to be composed of pseudo-tetragonal mullite aggregates enclosing elongated or round shaped alumina grains. After annealing the fibre at 1400°C the mullite structure became orthorhombic while losing alumina. A small increase of the Young modulus was observed because of the change of relative amounts of alumina and mullite and a diminution of the porosity. Thanks to its original microstructure the fibre was found to have a reduced creep rate when compared to other polycristalline oxide fibres but it was found to be extremely sensitive to external conditions and to suffer from premature failure due to slow crack growth (SCG).

Keywords

Alumina, mullite, fibres, nanocomposites, creep.