Synthesis and Characterization of Ni metal/MnFe₂O₄ Nanocomposites

Abstract

This thesis presents systematic research on nickel metal manganese ferrite nanocomposites (Ni-MnFe₂O₄) synthesized by the hydrothermal method at a temperature of 120 °C and a synthesis time of 20s hours. The optical and structural properties were investigated using X-ray Diffraction (XRD), Raman Spectroscopy, and the UVVisible spectroscopy method. In all prepared samples, ferrites phase corresponds to cubic spinel structure (space group Fd-3m) and Ni metals correspond to face centred cubic structure. Simultaneous existence of distinct and sharp peaks of Mn ferrite and Ni metal showed successfully synthesis of nanocomposite. The crystallite size, micro strain and lattice constant were determined for both phase (ferrite and metal) using XRD data. The average values of crystallite size, micro strain, and lattice constant for Manganese ferrite are approximately 27.3551 nm, 0.004174 ε and 8.48760 Å respectively. For nickel metal the average values of crystallite size, micro strain, and lattice constant are 29.69734 nm, 0.002683, and 3.5237 Å respectively. Five typical modes of spinel (A1g +Eg+3T2g) appeared in Raman spectra between 200 and 800 cm-1. The primary A1g mode at 640 cm-1 was blue-shifted by 7 cm-1 as the Ni content increased, indicating that the Fe-O bond covalency was increased at the octahedral sites. UV-Vis Photo spectroscopy was employed to determine the optical characteristic of prepared nanocomposites from UV-Vis spectroscopy analysis, direct bandgap of value 1.22 eV for Mn Ferrite sample and 1.10 eV for composites samples due to Ni₃d-O₂p charge transfers. The (Ni-MnFe₂O₄) composition exhibited distinct features, including a crystallite size and a maximum bandgap, indicating the relevance of strong quantum confinement. All this evidence demonstrates that the structural and optical properties can be controlled accurately through nickel substitution, making Ni- Mn ferrites interesting materials for application in photocatalytic and magneto-optical fields.