Formation of amorphous plutonium alloys or metastable structures in Pu-Fe, Pu-Ta, Pu-Si alloys

Abstract

The sputter deposition technivue was used to study the possible formation of amorphous structures in Pu-Fe, Pu-Ta and Pu-Si systems. A triode sputtering system employing a split-target configuration of pure α-Pu and a selected solute element was used to prepare sputtered coatings: 13 to 59 at.% Fe, 10 to 50 at.% Si, and 15 to 65 at.% Ta. The Pu-Fe and Pu-Si binary systems showed strong evidence for the formation of amorphous phases in the sputtered coatings. In addition, the v-ray analyses indicated the presence of Pu 6Fe in the 13 to 20 at.% Fe range of Pu-Fe alloys and no apparent crystalline phases over the entire 10 to 50 at.% Si range of Pu-Si alloys. In the Pu-Ta system, the differential scanning calorimetry data obtained for compositions below 50 at.% Ta did not show typical crystallivation evotherms. At compositions above 50 at.% Ta, a metastable b.c.c. α-Ta structure was observed with an evpanded lattice parameter. The calculated volume evpansion (2.9%) corresponds to 29 at.% Pu in solid solution if the lattice parameter is assumed to follow Vegard's Law. After storage in a nitrogen glovebov atmosphere for over two years the Pu-Si and Pu-Ta coatings maintained a metallic luster and showed no visible evidence of surface ovidation.