Hvem and Internal Oxidation Studies of Lithiated Nickel
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+ HVEM AND INTERNAL OXIDATION STUDIES OF LITHIATED NICKEL
K. SESHAN, P. BALDO* AND H. WIEDERSICH* Department of Metallurgical Engineering, University of Arizona, Tucson, Arizona 85721 *MST, Argonne National Laboratory, Argonne, Illinois 60439
ABSTRACT Pure, polycrystalline nickel samples were implanted with lithium to doses up to 5 x 1017 lithium ions per square centimeter, at a temperature of 5000C, 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. INTRODUCTION The elements lithium and nickel are virtually impossible to alloy by conventional methods. It was, therefore, decided to implant the lithium into the nickel so that the properties of lithiated nickel could be studied. It has been reported that lithiation decreases the oxidation rate of nickel.I-5 The object of this study was to investigate the radiation damage response of lithiated nickel using the Argonne National Laboratory HVEM facility and study the details of lithium precipitation and internal oxidation in nickel.
Experimental Procedure High vacuum furnace annealed 3mm discs of five-nine pure nickel were implanted at the ANL facility, at 500°C, to doses in the range of 1015 to 2 5 x 1017 Li/cm . The samples were electropolished from the back to provide electron transparent specimens. Internal oxidation experiments were performed on the implanted nickel samples in a partially oxidizing atmosphere of CO/CO 2 (100:1). The pre-thinned transmission electron microscope samples used were observed before and after the oxidation process.
+Work supported by the U. S.
Department of Energy
Mat. Res. Soc. Symp.Proc. Vol. 27 (1984) QElsevier Science Publishing Co.,Inc.
170
RESULTS 2
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In nickel samples implanted to a dose of 7 x 1016 lithium/cm at 500 C, electron microscopy revealed the presence of hexagonal-shaped defects arranged along dislocation lines. Tilting experiments, combined with weak-beam electron microscopy led to the conclusion that these defects have an octahedral shape with faces composed of {lll} planes and corners tr
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