The reaction of ceria coatings on mica with H 2S : An in-situ X-ray diffraction study

Abstract

Thin layers of ceria were deposited on the surface of mica platelets in solution. The reaction of such particles with hydrogen sulfide yields a red colored special effect pigment. The ceria layer reacts with H 2S to produce a variety of sulfide and oxysulfide phases. The reaction path discovered in situ by time and temperature resolved X-ray diffraction is CeO 2→CeS 2→C-Ce 2S 3→Ce 10S 14O. The reaction itself is extremely variable depending on gas flow, heating rates and decomposition atmospheres. Effects on the thin film are recorded by scanning electron microscopy (SEM) and revealed a destruction of the layer once red Ce 10S 14O was formed. The product layer then reveals the typical nonwetting behaviour of a liquid on a surface.