Regulated color-changing metallic glasses

Abstract A new type of color-changing metals is discovered: the color on these metals can change continuously and spontaneously under ambient conditions. The colors are created mostly by the light interference in the surface metallic-oxide layer and partially by the optical bandgap energy of the formed yttrium-doped cerium oxide. Although metal oxidation is a natural consequence for most metals, this series of the yttrium-doped and cerium-based metallic glasses are special because i) the oxidation is continuous, allowing color-changing; ii) the oxide layer is uniform in thickness avoiding stain and corrosion; iii) the colors are changed as fast as in days. The color-changing functionality is greatly connected to the oxygen affinity of the cerium constituent, the glassy structure devoid of grain boundaries, and the regulation from the yttrium dopant. This work not only demonstrates a new direction for metal oxidation but also points out new applications of metallic glass.