High-temperature reactivity and wetting characteristics of Al/ZnO system related to the zinc oxide single crystal orientation

Abstract

Wettability and reactivity of the Al/ZnO couple at a temperature of 1273 K in vacuum have been studied with application of modified sessile drop method. The results obtained for the ZnO single crystal substrates of various orientations evidenced non-wetting by liquid aluminium, showing high contact angles of 100°–107°. Detailed transmission electron microscopy characterization unambiguously proved that the creation of two interfacial layers revealing highly epitaxial growth took place at high-temperature interaction between liquid Al drop and ZnO substrate. The layers of columnar grains consisted of reactively formed Al2O3 and ZnAl2O4, the second one growing at the expense of the alumina. The alumina was identified as either cubic γ-, tetragonal δ- or monoclinic λ-Al2O3, depending on subtle changes in chemistry of the surface top layer of the ZnO substrates.