Surface composition of liquid metals and alloys

In order to characterize the surfaces of liquids proposed for use as plasma-facing materials in fusion reactors, the techniques of low-energy ion scattering and direct recoil spectroscopy have been used to examine the surface compositions of liquid Li, Ga, Sn, and a Sn–Li alloy in vacuum as a function of temperature. Oxygen is found to segregate to the surface of several metallic liquids. In the case of a Sn–Li alloy, Li also segregates to the liquid surface. Molecular hydrogen and its isotopes readily adsorb on Li surfaces, but not on those of Ga or Sn. Hydrogenic atoms at thermal energies can adsorb on both Li and Ga, but no evidence has been found for hydrogen isotopes residing at the surface of liquid Sn from the melting temperature to 800 ∘C.