Phase transformation of Cu@Ag core-shell nanoparticles upon heating

In this study, the structural evolution and oxidation of Cu@Ag core-shell nanoparticle deposits (with average particle diameter of 25 nm and Ag/Cu atomic ratio of 1/8) upon heating in air were investigated quantitatively via in situ synchrotron radiation X-ray diffraction. With an increasing temperature, the coalescence of Cu cores and ripening of Ag shell occurred simultansously, resulting in discrere Ag nanonodules and unprotected Cu microparticles. Due to the protection by thin Ag shell, the formation temperatures of the Cu oxides for Cu@Ag NPs were higher than those of pure Cu nanoparticles with similar size by at least 150 °C.