Physicochemical Structure of Carburized Thoriated Tungsten and Its Effect on Thermionic Emission

The work presented here aims to optimize parameters for emission current and lifetime based on thermionic, microstructural and chemical characterization. Carburization was performed using toluene in a test structure consisting of a straight 0.006-inch diameter 2% thoria-tungsten wire, tensioned with a leaf spring and concentric to the inner diameter of a 1-inch long, 0.250-inch diameter molybdenum tube serving as the anode for emission testing. Scanning electron microscope/energy dispersive spectroscopy analysis shows the formation of a similar to 5 mu m carburization layer, while thermionic measurements show improved emission over uncarburized thoriated tungsten.