Synthesis of a alumina/barium aluminosilicate oxyde/oxyde composite at reduced temperature?
SAINTONGE A. 1, LEPETITCORPS Y. 1, ALLEMAND A. 2, BRAUN J. 1,3, PIQUERO T. 3, BEAUDET - SAVIGNAT S. 3
1 Thermostructural Composites Laboratory UMR 5801, Pessac, F-33600, France; 2 CEA CESTA, F-33116, Le Barp, France; 3 CEA DAM Le Ripault, F-37260, Monts, France
Ceramics are now present in many advanced applications thanks to their high temperature properties. Their low toughness could be improved by developing fiber-reinforced ceramic matrix materials. Thus, these composite materials will combine lightness and mechanical resistance induced by the fibers, with the refractory character of a ceramic matrix. The field of application of these ceramic matrix composites is increasingly broad and corresponds to the requirements of the aeronautical and space industries. That is why the study of these thermostructural composites, and in particular ceramic matrix composites (CMC), is crucial. Currently, SiO2 / SiO2 and Al2O3 / Al2O3 composites are already commonly used. Barium aluminosilicate or BAS (BaAl2Si2O8) has been lately aroused interest as matrix material because their properties can largely compete with composites already used , , among others oxide matrices reinforced with alumina fibers. BAS hexagonal phase, thermodynamically stable between 1590°C and its melting point (1750°C), has a coefficient of thermal expansion comparable to alumina fibers. Unfortunately, the latter lose their mechanical properties at such temperatures. Therefore, the challenge of this work is to develop a barium aluminosilicate matrix composite (BAS) with alumina fibers at lower temperature (up to 1300°C).
To reach this challenge, investigations have been concentrated on the synthesis of such composite with a complex architecture of fibrous reinforcement and on the evaluation of its properties. The study will therefore focus on two developments:
- Firstly, an impregnation process in the aim to produce a ceramic matrix composite.
- Secondly, a conventional sintering method leading to the cohesion of the composite without destabilizing the hexagonal phase of the matrix and without damaging the fibrous reinforcement. The identification and the use of additives sintering turn out to be favorable to the latter points.
 Narottam P. Bansal, Handbook of Ceramic Composites, vol. 11. 2005. ? F. Ye, J. C. Gu, Y. Zhou, and M. Iwasa, “Synthesis of BaAl2Si2O8 glass-ceramic by a sol-gel method and the fabrication of SiCpl/ BaAl2Si2O8 composites,” J Eur Ceram Soc, vol. 23, no. 13, pp. 2203–2209, 2003.