Influence of Cu content on the fractal and multifractal properties of Zn-Mg-Cu composites

In this work, the morphology and fractal properties of Zn-Mg and Zn-Mg-Cu nanocomposites were investigated. Zn-Mg-Cu nanocomposites with 2, 3 and 4% by weight of Cu were prepared by electrochemical method on FTO glass substrate and compared with Zn-Mg nanocomposite. The surface properties of the nanocomposites were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM images confirm that the morphology and grain size depend on the amount of Cu doping. The grain size decreases with increasing Cu concentration. Statistical analysis based on 3D AFM images showed that surface roughness (S-q) and fractal dimension (D-f) decreased with increasing Cu concentration. D-f obtained using the log(count) vs. log(box size) curve showed that D-f is independent of scan size and pixel resolution. The D-f values of ZM3, ZM3C2, ZM3C3 and ZM3C4 were calculated to be 2.48, 2.44, 2.36 and 2.30, respectively. It can be concluded that the lacunarity coefficient beta of all the nanocomposites has a high degree of surface microstructure homogeneity with beta < 0.07. Multifractal behaviour was observed for all nanocomposites, with the multifractal degree of Zn-Mg-Cu nanocomposites being reduced compared to that of Zn-Mg nanocomposites.