Atomic structures and compositions of internal interfaces

Abstract

Listen

Translate article

The emphasis during the past year has been on reproducibly obtaining metal/metal oxide interfaces in a number of binary alloy systems that are suitable for combined transmission electron and atom probe field-ion microscopy, as well as analytical electron microscopy. This requires obtaining a high number density (N{sub d})(<5{center dot}10{sup 16} cm{sup {minus}3}) of a small metal-oxide precipitates (1 to 20 nm diam) in wire specimens. These requirements are essential, as the primary goal of our initial research to study the chemical compositions of metal/metal oxide interfaces on an atomic scale using the atom-probe technique. The basic approach we are employing is to prepare binary metal alloys, for which the solute species has a greater affinity for oxygen than the solvent, and where the permeability of the oxygen (c{sub O}D{sub O}) is greater than c{sub s}D{sub s} for the solute (s) elements. The specific systems presently being investigated are: (1) Pt-4 at. % W and Pt-8.5 at. % W; (2) Cu-0.1 wt. % and Cu-1.3 at. % Mg; (3) Cu-2.7 at. % Co; (4) Pt-9.15 wt. % Co; and (5) Ni-20 wt. % Cr. Internal oxide precipitates of MgO and CoO -- in Cu(Mg) and Cu(Co) alloys -- have been obtainedmore » at values of N{sub d} and precipitate diameter that are suitable for combined transmission electron microscope and atom probe studies. Also results have been obtained which indicate that internal oxides of Cr{sub 2}O{sub 3} in a Ni(Cr) alloy and CoO in a Pt(Co) alloy should be suitable for our experimental program. 21 refs., 3 figs., 2 tabs.« less