Nanoscale 3D Spatial Analysis of Zirconia Disc Surfaces Subjected to Different Laser Treatments

We propose the application of morphological, fractal and multifractal analysis to differentiate surface patterns on zirconia-based ceramics after laser treatments. Furthermore, we introduce two new approaches for ceramic surfaces: the Moran correlogram, which complements the spatial autocorrelation analyses, and the Otsu binarization algorithm, which was used to identify the lacunar points in the lacunarity analysis. First, the AFM (Atomic Force Microscope) topographies revealed that samples have significant differences in terms of spatial features. Quantitatively, spatial surface texture parameters indicated that all laser treatments reduced the superficial isotropy of the Zirconia disc. Moran's correlograms revealed a decrease in the short-range correlation in all treated samples. The Minkowski functionals (MFs) indicated a reduction in the amount of matter in the peaks, especially for the sample with Nd-YAG laser treatment. The estimated fractal dimension (FD) pointed out that all laser treatments weakened the surface complexity of the Zirconia disc. On the other hand, clear fingerprints of multifractal behavior in all the samples were detected, where the highest degree of multifractality was computed for the samples with CO2 laser treatment. Finally, our findings suggested that the morphological changes caused by laser treatments on the surfaces of zirconia discs can be monitored and differentiated through the parameters proposed here.