Hvem and Internal Oxidation Studies of Lithiated Nickel

Abstract

Pure, polycrystalline nickel samples were implanted with lithium to doses up to 5 × 10¹⁷ lithium ions per square centimeter, at a temperature of 500°C, such that the implantation damage would anneal. These samples were then prepared for electron microscopy and examined at 1 MeV, in the Argonne National Laboratory HVEM facility. It was observed that compared to pure nickel, the lithium implanted nickel showed a different radiation damage behaviour. A plausible explanation for the difference in behaviour is presented in this paper.

The lithium implanted nickel, in the high dose samples, also showed an unusual form of precipitation. Electron microscopy revealed the precipitates to have truncated octahedral shapes with {111} planes for sides and {100} planes truncating the corners. They resemble voids and helium bubbles in nickel. The precipitates appear to be associated with dislocations. The lithium implanted nickel was internally oxidized in order to obtain evidence for the presence of lithium. Electron diffraction analysis of the internally oxidized lithiated nickel showed the presence of a topo-taxial compound being formed, with an ordered NaCl-structure. Possible interpretations of this diffraction pattern are discussed.