“DESIGN AND EVALUATION OF HIGH EMISSIVITY COATINGS FOR CARBON/CARBON COMPOSITES”

Abdullah Al Saad, MSE PhD Candidate 

Advisors: Professor Carlos Martinez and Professor Rodney Trice

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ABSTRACT

During re-entry, the hypersonic leading edges can experience enormous heat fluxes, with surface temperatures greater than 1600℃ expected. While carbon/carbon (C/C) is a candidate material for leading edge structures, it is prone to ablation damage above 500℃. Ablation-resistant coatings can protect the C/C, while emittance can be engineered to lower the leading-edge surface temperature via radiative cooling. In this dissertation, a novel bilayer coating system and a multilayer coating system based on individual layers consisting of ultra-high temperature ceramics (borides, carbides,) refractory oxides such as zirconia, and rare-earth oxide as emissivity modifiers is being applied to a C/C surface via pack cementation and plasma spray. Ablation tests are performed to evaluate the efficacy of the multilayer coatings in simulated high heat flux environments. A radiometric emissometer is developed to measure the spectral emittance of the coating surface at high temperatures up to 1500℃. The outcome of these experiments will help optimize the design of protective, high emittance coatings for C/C composites.