High Thermal - Stability Reaction Bonded SiC CMCs

Fracture tough forms of Silicon Carbide (SiC) have applications ranging from athermal optical instrumentation where high specific stiffness and thermal stability are required to maintain alignment of lightweighted optical instrumentation in space to gas turbine engines where fiber reinforced SiC needs to withstand high temperatures and oxidizing atmospheres. In the proposed effort SSG will combine our low-cost, reaction-bonded SiC (demonstrated material properties and near-net-shape design flexibility) with advanced SiC fiber to create a new ceramic matrix composite (CMC). The CMC material will enable passive thermal management of the entire optical instrument including lightweighted reflective optics and metering structure. Commercially available SiC fibers with high thermal conductivity and high temperature resistance will be coated with a novel boron-aluminum-nitride (BAN). The coated fiber will allow integration of fiber reinforcement in the RB SiC fabrication process. The BAN coating provides oxidation protection for long-fiber reinforced CMCs because it forms refractory aluminum borates upon oxidation, which seals cracks in the matrix or along the fiber/matrix interface. In Phase I SSG, will demonstrate the viability of combining RB SiC with BAN coated high temperature SiC fibers to form high thermal stability CMCs. Phase II will design and fabricate an athermal all RB SiC CMC telescope.