In the aircraft industry, Re is also used as a coating for face seal rotors, in air turbine starter components for gas turbine engines, as a diffusion barrier (e.g., on top of graphite), and as an alloying element in a Ni3Al-based superalloy for vanes and in a niobium (Nb)-based alloy for advanced jet engines.It is also used in nuclear reactors as a barrier between the uranium nitride nuclear fuel and the Nb alloy cladding.