Abstract
XPS and NMR were used to study the effect of sulfur and crystallinity on the transformation of Nanoporous alumina membranes prepared by anodic oxidation using sulfuric acid electrolyte. The transformation temperature at ca. 1250°C is influenced by the pore size, presumably due the critical crystallite (domain) size necessary to develop the stable α-Al2O3. NMR results also support that samples with larger pores contain poorly crystalline phases. In XPS study, Ar+ ion etching was performed on the sample to etch the surface at a rate of 3 nm min-1. As a result, sulfur was found to be concentrated within a depth of 3 nm from the surface. The S content of the surface was found to decrease to about one-fourth at a depth of ca 10 nm.
