Core shell coatings for nuclear thermal propulsion cermets

Abstract

Magnetron sputtering has been employed to provide conformal tungsten coatings from approximately 70 to 540 nm thicknesses over yttria stabilized zirconia (YSZ) powders. Through a rotating vessel, the powder was continually cascaded exposing its surface enabling the line-of-sight cathode tungsten target to deposit over the entire surface. With increasing coating thickness, a particulate surface morphology developed. These tungsten particulates were plate-like in morphology and faceted in some cases. The formation of these features is contributed to the continual low energy impacts between the hard YSZ powders during deposition as well as the adhesion and de-adhesion of the coatings connecting particle clusters. The results of this work demonstrate the ability of sputter deposition to create refractory coatings for cermet fuels utilized in nuclear thermal propulsion, as well as broader applications where core-shell powder fabrication is needed.