Hydrothermal facile fabrication of superhydrophobic magnetic nanospiky nickel wires: Optimization via statistical design

Abstract In the present research, novel superhydrophobic magnetic nanospiky nickel wires via a controlled one-step hydrothermal method were fabricated using Taguchi L16 statistical design. The effects of independent factors including concentration of NiCl2 .6H2O (50-125 mM), the concentration of N2H4.H2O (450-1650 mM), reaction temperature (80-100 oC), and reaction time (6-12 h) on the wettability properties of octadecyl trichlorosilane (ODTS)-modified samples were investigated. Based on ANOVA and the main effect analyses, despite all factors affecting the wettability response, hydrazine solution concentration with a contribution percent of 47.22% had the most significant effect on the samples' hydrophobicity and growth mechanism as a reducing agent and bridging bidentate ligand. Under the predicted optimum conditions ( A 1 ¯ , B 3 ¯ , C 2 ¯ , D 2 ¯ ), the water contact angle (WCA) and contact angle hysteresis (CAH) were 162.78°±2.4o and 4.32°±0.9o, respectively. Morphological aspects and chemical composition of the as-prepared samples were studied using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), and Vibrating Sample Magnetometer (VSM) analyses. According to the FESEM images, the length and spike diameters were ranged 500-800 nm and 50-90 nm, respectively. The conical nanospikes' growth on the nickel wires was not dependent on the external magnetic field. It just promoted the formation of straight wires along the present magnetic field. The coercivity (Hc) and remnant magnetism (Mr) in the presence of the magnetic field were 103.077 Oe and 7.80 emu/g, respectively, due to the crystallite arrangement anisotropy.