| Abstrakt: |
Extensive regions of Liesegang bands, or periodic precipitation, are observed in composite materials prepared by the internal oxidation of Ag-9 Cd alloys containing small amounts of certain metallic elements: Al, Be, Mg, Sc, and Y. The elements which induce this form of distribution of oxide particles possess the following characteristics: relatively small atomic radius (less than 1.80Å), high oxidation potential (higher than 1.66 v), and some solid solubility in silver at 800°C. In this solid-state system the constancy of the spacing coefficient, the ratio of distances from the surface of consecutive bands, is generally satisfied. The spacing coefficient is found to be dependent on a) the specific additive, b) the concentration of the additive, c) the concentration of the oxygen, and in some case d) the crystal orientation. [ABSTRACT FROM AUTHOR] |
