Formation and analysis of amorphous and nanocrystalline phases in Al–Cu–Mg alloy under friction stir processing

Homogeneous amorphous and nanocrystalline phases formed in the nugget zone of a friction stir-processed Al–Cu–Mg alloy have been studied. X-ray diffraction analysis indicated a diffuse scattering peak with characteristics of an amorphous phase existed in the range 15°–29°. Further, TEM analysis proved the existence of an amorphous structure. Friction stir processing provides special physical conditions, such as high temperature, high hydrostatic pressure and large shear stress, which could induce the amorphization of the alloy.     

Pressure-induced phase transition in nanocrystalline La0.9Mn0.8Fe0.2O3.15 perovskite studied by Mössbauer spectroscopy

We report here on a pressure-induced phase transition in nanocrystalline La-deficient perovskite oxide, synthesised through the sol–gel technique, using Mössbauer spectroscopy, electrical resistivity and X-ray diffraction measurements at room temperature. At ambient pressure, the high-spin Fe³⁺ ion is distributed in two different environments. Below 0.6 GPa, a sudden dip in the resistivity curve and a single-environment Fe³⁺ doublet in the Mössbauer pattern are indicative of lattice compaction. A high-spin to low-spin Fe³⁺ transition at 2.1 GPa, and an orthorhombic to monoclinic structural transformation at 4.9 GPa, as revealed through Mössbauer patterns, are also associated with sudden dips in the electrical resistivity. X-ray diffraction patterns support the results.     

Morphological and magnetic response of copper-substituted nickel ferrite nanoparticles

Ferrite nanoparticles are interesting materials owing to their unique physical and chemical properties. The metal-doped ferrites have well-defined structures and magnetic response, such as high permeability for a specific frequency range. In this study, copper-substituted nickel ferrite (Ni_1?xCu_xFe₂O₄) nanoparticles with a compositional range of 0?≤?x?≤?0.3 were synthesised through a co-precipitation technique. Metal chlorides were used as precursors and NaOH as a precipitating agent for the growth of ferrite nanoparticles. To minimise the internal stresses and maximise the magnetic response, ferrite nanoparticles were annealed in a furnace at 700°C for 6 h. The structural and magnetic response of Ni_1?xCu_xFe₂O₄ ferrite with different values of x were investigated using Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy (FT-IR), Vibrating Sample Magnetometer (VSM) and X-ray Diffraction (XRD) techniques. XRD analysis confirmed the formation of cubic spinel structure of single phase for all the compositions. The lattice constant decreased with increase in the value of x. FT-IR study showed two main metal oxygen bonds in the range 500–700 cm^?1 confirming the formation of a single-phase cubic inverse structure of Cu-substituted Ni ferrite. VSM results revealed the formation of ferrimagnetic nanoparticles. The optical and magnetic response of the ferrite nanoparticles changed with Cu content.