Ceramic-Metal Interfaces by Functional Grading

Glacigen Materials proposes a novel technique for producing large-area sheets of functionally graded materials (FGM), which yield robust ceramic-metal interfaces capable of withstanding harsh environments that include high temperatures. Propulsion systems offer some of the harshest possible design conditions from a materials perspective and the demands placed on engineering materials will become more rigorous in future systems. The combination of structural and environmental constraints often dictate that ceramics and metals be used synergistically. Unfortunately, the limitations of ceramic-metal joining are exacerbated in these same environments where simultaneous use of ceramics and metals would be most useful. Large discrepancies in thermal expansion coefficients and near-planar interfaces lead to delamination and spallation even in the best engineered bonds. As a novel approach to this problem, Glacigen will create robust C-M interfaces by grading from one material phase to the other through a tailorable thickness. The technique is materials flexible, enjoys exceptional damage tolerance, and can accept significant mismatches in thermal expansion coefficients. The method for producing FGM sheets presented in this proposal will have the added advantage of controlled anisotropic properties within the sheets. In particular, it is anticipated that this new material system will be particularly valued for its damage tolerance at the interface where up to 96% of the interface can be destroyed before contact area is reduced to that of a planar joint with the same footprint. A second point of unique value will lie in the utility of engineered anisotropy where through thickness thermal conductivity is expected to be dramatically higher than in-plane thermal conductivity. Phase I efforts will demonstrate fabrication of these sheets and will include the characterization of mechanical, thermal, and functional properties.