POROUS RARE-EARTH ALUMINATE FIBER COATINGS FOR OXIDE-OXIDE COMPOSITES

摘要

A porous-oxide fiber coating concept was investigated for oxide matrices reinforced with Nextel~(TM) 610 fibers. Polymeric-solution-derived lanthanum hexaluminate (LaMnAl_(11)O_(19)) with a fugitive carbon phase and yttrium-aluminum garnet (YAG, Y_3Al_5O_(12)) with a fugitive carbon phase were chosen as porous fiber coatings. Matrices of Blackglas~(TM) or alumina were used to form minicomposites. Ultimate tensile strengths were used to evaluate the effect of the porous coatings on tow and minicomposite strengths. The porous lanthanum hexaluminate coating resulted in tow strength degradation of approx 40 percent. The porous YAG coatings did not reduce the strength of the tow when heated in argon and degraded the tow strength by only approx 15 percent after heating in air to 1200 deg C for 2 h. Both rare-earth aluminate porous coatings greatly increased the strengths of minicomposites over control minicomposites with no fiber coating.