Daliang Liu

Self-formation of nanocomposite Cu/Al2O3 thin films on CuAl dilute alloys by annealing in inert atmospheres

Self-formation of the surface protective layer on dilute CuAl alloys by annealing in inert atmospheres is investigated with thermodynamic consideration, first principles density functional simulation, and transmission electron microscopy (TEM). The calculations predict that when Cu atoms are involved in the surface Al2O3 layer, the Cu-Al2O3 solution does not exist. Instead, a phase structure of Cu and Al2O3 should be formed. Consistent with this prediction, TEM observations showed that the surface thin film consists of the nanocomposite Cu/Al2O3 structure, in which spherical Cu nanoparticles 3–5 nm in diameter are formed and disperse in the amorphous Al2O3 matrix. The results are discussed with respect to surface segregation and the stability of Cu in Al2O3.