Abstract: A graphite fiber reinforced silica matrix composite comprising a plurality of graphite fibers bonded together in a silica matrix comprised of silica, boron phosphate and beta-spodumene modified with a minor amount of an alkaline earth metal oxide is disclosed. The extremely low, nearly zero, coefficient of thermal expansion coupled with the moderate thermal conductivity and low density of the composite make the composite particularly suitable as a substrate material for high energy laser mirrors.

Abstract: A ceramic broadband radome is provided, comprising alternating layers of silicon nitride and fused silica, including a layer of silicon nitride at both outer and inner surfaces of the radome wall and at least one additional layer of silicon nitride within the wall. Elevated temperature processing is used to form an in situ prestressed condition. Resistance to stresses induced by thermal differentials, rain erosion, particle impact, aerodynamic loads and crack propagation is improved over other monolithic and sandwich ceramic radomes, while high transmission efficiency is maintained over a wide band of radar frequencies.