Optimization of the structural and magnetic properties of the electrodeposited Ni–Fe–P coatings using ANOVA and response surface methods

Abstract

Ni–Fe–P coatings have been successfully electrodeposited from Iron-Nickel sulfate bath under several conditions: Fe/Ni molar ratio (0.1–0.5), current density (15–55 mA cm−2) and solution pH (2–4). The chemical composition, morphology, structure and magnetic properties of the deposits were studied using SEM-EDX, XRD and AGFM techniques. The EDX results showed that the Ni–Fe–P coatings can be classified into two categories named low Fe content and high Fe content. Magnetic hysteresis loops displayed a soft magnetic character for all the deposited coatings. XRD and AGFM results revealed that the High Fe content coatings present a crystalline structure and high saturation magnetization, Ms, while those with low Fe content exhibited an amorphous structure with low Ms values. The central composite design (CCD) methodology using the ANalysis Of VAriances (ANOVA) and the Response Surface Methodology (RSM) have been applied to investigate the main and the interaction effects of several electroplating parameters on the crystalline phase proportion, CP, and the saturation magnetization, Ms, of the deposits. The ANOVA results showed that Fe/Ni ratio and pH are the most significant factors on the studied properties. A relationship between the factors and the studied responses (CP and Ms) has been established via a linear and quadratic model. A perfect agreement between the experimental and the predicted values is confirmed by high correlation coefficient values: R2 = 0.97 for CP and 0.92 for Ms. The optimal factors required for the best properties of Fe–Ni–P coatings have been determined by the desirability function.