Changes in Cu-silica interfacial chemistry with oxygen chemical potential

Interfacial chemistry and equilibrium morphology of SiO2 glass precipitates in a solid copper matrix are studied as a function of the oxygen chemical potential. Spherical SiO2-glass precipitates are formed within copper by internal oxidation of (Cu,Si) single crystals at different oxygen activities. The metal-glass interfaces are rough at an atomic level. Atomic and electronic structures of the different interfaces are analyzed by high spatial resolution EELS. At high oxygen activity, two interfacial zones with specific electronic states are distinguished: on the metal-side of the interface, the correlated modifications in the O-1s and Cu-2p edges indicate O-2p-Cu-3d hybridization; on the glass-side of the interface, a modification of the Cu-2p edge is observed, which is interpreted in terms of a weak interaction of highly perturbed metallic copper with the constituents of the adjacent glass network. At intermediate oxygen activity, only the latter modification is observed at the interface. Oxygen adsorption and desorption to the silica-copper interface are modeled by a continuum approach; model results are compared to those obtained by experiments. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.