Processing and mechanical behavior of Nicalon/SiC and Nextel/SiC composites with sol-gel derived oxide interfacial coatings.

摘要

Mullite and aluminum titanate precursor sols were developed for coating applications. High temperature X-ray diffraction studies in air identified that mullite crystallizes between 950;To study the effect of protecting the fibers by an inert material during sol-gel oxide coating, oxide/C, and C/oxide/C interfaces were considered for Nicalon/SiC and Nextel/SiC composites. Since composites with C/oxide/C interfaces exhibited higher flexural strengths than composites with oxide/C interfaces in the as-processed condition, C/oxide/C interfaces were studied. Also, Nicalon/SiC composites with C/oxide/C interfaces retained damage-tolerant behavior and substantial amount of their as-processed strengths even after 24 h oxidation at 1000;Nicalon/SiC composites with C and C/oxide/C interfaces were fabricated and flexure tested at room temperature in both as-processed and oxidized conditions. Flexural strengths of the composites with C, and C/oxide/C interfaces decreased with increasing exposure time at 1000