Bi-fractal dimension description- Inferring topography alteration of an asphaltene deposited heterogeneous surface

Using AFM (Atomic Force Microscopy) and SEM (Scanning Electron Microscopy) images are common applied methods to investigate homogeneous surface topography. Fractal analysis of the images provides fractal dimension of the surface which is used for heterogeneous surface indices. Precipitation of organic materials on a rough surface and its irregular growth result in morphology changes and converts a homogeneous surface to a heterogeneous one. In this paper, the topography alteration of a glass surface as a result of asphaltene precipitation and its growth at various pressures was investigated by bi-fractal approach. Two different regions on the deposited surfaces were observed. Thesetwo regions named micro asperities (Zone I) and macro asperities (Zone II) namely. And the fractal dimension of each zone was calculated. The topography information of the surfaces was obtained by two image analyses. The bi-fractal analysis demonstrated that topography alteration in zone II (macro asperities) is more evident than that in zone I (micro asperities) and a better correlation was observed between the fractal dimensions inferred from the AFM images (DA) than the SEM images (DS).

Keywords:

Bi-fractal , surface roughness , AFM , SEM , topography