Surfactant protective layers on the surface of nanocrystalline iron particles

The surface structure of stabilized iron particles obtained at the different stages of high temperature reduction in a hydrogen flow has been studied. Oleic acid (OA) was used as a stabilizing agent. For comparison, hexamethylenediamine (HMA) and acrylamide (AA) were also taken as stabilizers. The interface between the particle surface and the OA-based stabilizing layer is characterized by the presence of different oxide phases. The structure of the particle surface layer will influence the process of the OA-adsorption and, as a consequence, the formation of the stabilizing coating. The main part of HMA adsorbs molecularly, a small part of molecules only adsorbing through dissociation with the formation of coordinative complex at the interface. Only one amine group takes part in the adsorption interaction. AA, as such, does not take part in the formation of the stabilizing layer, but it is in all probability a promoter of Fe2O3 layer formation at the particle surface, which provides the best corrosion resistance of the particles.