Surendhiran Srinivasan

Nickel oxide nanoparticles (NiO NPs), Magnesium oxide nanoparticles (MgO NPs), and MgNiO ₂ ternary metal oxide nanoparticles (MN NPs) were prepared using a green method that employed Sonneratia ovata leaf extract. X‐ray diffraction (XRD) results validated the cubic structure, revealing typical crystallite sizes of 10.01 nm for NiO, 22.67 nm for MgO, and 14.82 nm for MN NPs. Fourier transform infrared (FTIR) spectra identified functional groups in both metal oxides and phytochemicals, whereas the optical results indicated absorption edges at 307 nm (NiO), 214 nm (MgO), and 288 nm (MN NPs). Morphological and particle‐size analyses revealed uniformly distributed nanostructures with average particle sizes of 20.73, 38.55, and 25.38 nm. The elemental mapping confirmed the uniform incorporation of Ni, Mg, and O, whereas X‐ray photoelectron spectra (XPS) revealed the oxidation states Ni ²⁺ and Mg ²⁺ on oxygen‐rich surfaces. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) revealed improved charge transfer, reduced resistance, and enhanced redox reversibility in MN NPs compared with the individual oxides. Photocatalytic analyses conducted under sunlight using a dye concentration of 10 mg/L and a catalyst dosage of 1 g/L revealed that MN NPs exhibited the highest degradation efficiencies for Congo red (98.95%), Crystal violet (95.26%), and paracetamol (99.07%), following pseudo‐first‐order kinetics, while recycling tests demonstrated significant stability (>92% efficiency after five cycles). The findings indicate that the synergistic structural formation between NiO and MgO enhances charge separation, radical generation, and pollutant mineralization, highlighting MN NPs as a cost‐effective and environmentally benign nanocatalyst for wastewater treatment and multifunctional applications.

Sol‐gel‐derived amorphous Al ₂ O ₃ ‐ZrO ₂ /SiO ₂ (AZS) and Al ₂ O ₃ ‐(Y ₂ O ₃ ) ZrO ₂ /SiO ₂ (AYZS) nanocomposite coatings were developed on stainless steel (SS) 316L specimens. The corrosion resistance of identical AZS and AYZS specimens in 5 wt.% HCl, H ₂ SO ₄ , and NaCl electrolytes was investigated using electrochemical polarization plots and impedance spectroscopy. The EIS results indicate that the corrosion resistance follows the order NaCl > H ₂ SO ₄ > HCl, with the highest charge‐transfer resistance observed in the NaCl electrolyte at low frequencies. Moreover, the lower current density observed in the NaCl and H ₂ SO ₄ electrolytes suggests that the coatings were relatively crack‐ and defect‐free, thereby providing superior corrosion protection. Surface‐coating stability, degradation, and corrosion products were observed using SEM and optical microscopy. The developed silica sol‐based AZS and AYZS ceramic coatings provide enhanced protection for metallic specimens in both acidic and alkaline environments.