Fractal dimension determined through optical and scanning electron microscopy on FeCrAl alloy after polishing, erosion, and oxidizing processes

Abstract

Optical and scanning electron microscopy (OM and SEM) are techniques that are normally used for 2D-analysis of surface features. By fractal dimension analysis of the gray-scale OM and SEM images, it is possible to get quantitative topographical measurements. In this work, three different surface topographies (polished, eroded, and oxidized) were analyzed on FeCrAl alloy by OM and SEM. Clear surface topographical changes can be qualitatively observed. In order to quantify such changes, two steps were followed: (i) a gray-scale digitalization from each image was used to reproduce topographical features on the analyzed surface, and (ii) from this information, the fractal dimension (D) was determined using fractal3e software. The fractal dimension determined in this form follows coherently the topographical changes produced on the FeCrAl alloy after polishing, erosion, and oxidizing processes. The variations of fractal dimension values against the temperature of the oxidizing processes reflect well the oxide growth changes. Moreover, a minimum D-value is registered at 750 8C, which corresponds to the d-u alumina phase transition temperature as determined by differential thermal analysis (DTA) on the same alloy.

Hallmarks of the Kardar–Parisi–Zhang universality class elicited by scanning probe microscopy

“…The SEM images were processed with a standard blur (lowpass) filter to erase the effects of electric accumulation in the grain borders. The gray-scale of SEM images was linearly converted to a height interval 0 ≤ h ≤ 1 [59]. Even though the vertical resolution cannot be obtained with SEM, the gray-scale method has been used to estimate fractal dimensions in semiconductor surfaces [59].…”

“…The gray-scale of SEM images was linearly converted to a height interval 0 ≤ h ≤ 1 [59]. Even though the vertical resolution cannot be obtained with SEM, the gray-scale method has been used to estimate fractal dimensions in semiconductor surfaces [59]. For our purpose, the actual height scale does not matter since distribution is shifted to zero mean and variance 1.…”