Chemical and Materials Sciences: Research Findings Vol. 4

Magnetic Ni-Co Nano particles are gaining significant attention due to their unique physical, chemical, and magnetic properties.  These properties have made them ideal candidates for several magnetic applications. In this study, a significant effort has been made to provide a deep analysis of the highly relevant and promising synthesis method (i.e., green synthesis by carambola fruit Juice modified oxalate method) while focusing on the possibility of modulating the morphology, particle size/ particle size distribution, and crystallinity of the final nanomaterial.  These parameters have a direct influence on the magnetic performance of the Nanomaterial. The general properties and particle morphology of nickel oxide / Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano-sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesised by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0, 0.1, 0.3, 0.5, 1, 3, 5.0, 40.0, and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterised by FT─IR to identify the functional groups present in the precipitate formed, while TGA/DTG was carried out to study the decomposition profile and  the decomposition temperature of the precursors. The precursors decomposed at 400 °C.  PXRD characterised the decomposition products to determine the phases, and SEM/TEM to determine the morphology. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/ nickel hydroxide (Co_xNi_1-xO//Ni (OH)₂) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous (Co_xNi_1-xO/Ni(OH)₂) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with an increase in the concentration of dopant atoms in the composite. The EDS results showed that only nickel, cobalt, Oxygen, carbon, and hydrogen were present in the decomposed samples. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties that correlated strongly with particle size, shape, and morphology. Observed values of retention (4.50 × 10⁻³ emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10⁻³ emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesised Cobalt-doped Nickel Oxide/ nickel hydroxide (Co_xNi_1-xO//Ni (OH)₂) Nano composites have potential applications in Magnetic memories and the hardness of magnetic materials.