Papers by Author: Z. Keresztes

Abstract: The layer formation of phosphonic acids on mica surface as a model system, from aqueous and ethanol solutions has been investigated. The aggregation behavior (critical micelle concentration, cmc) of molecules in the solution phase has been determined by surface tension measurements in order to select the appropriate concentration for the layer formation experiments. Layer formation of self-assembling molecules of alkyl-phosphonic acids has been followed by atomic force microscopy (AFM). Nucleation, growth and coalescence of densely packed islands of phosphonates from ethanol solution have been recorded on mica surface. The structure of islands depends on the length of alkyl-chains. Self-assembly of phosphonates has been also observed from aqueous solution, as presented by octyl-phosphonic acid (OcPA). The height of OcPA islands is 1.46 􀁲 0.22 nm, which is practically equal with the length of molecule (1.4 nm). This shows that OcPA molecules form monolayer height domains on the mica surface.

Abstract: Phosphonate layer formation on passive iron surface has been investigated by electrochemical and atomic force microscopy techniques. It was found that phosphonate groups bond more strongly to oxide surface, while metallic iron surface is disadvantageous for phosphonate layer formation in aqueous solutions. The rate of anodic dissolution is continually decreasing due to the time-dependent formation of protective phosphonate layer. The kinetics of phosphonate layer formation on passive iron is determined by the potential applied for preceding passive film formation. The size and shape of iron oxide grains depends slightly on the potential of passivation. Changes in morphology due to the phosphonate layer formation have been recorded by AFM.