Effect of isochronal annealing on phase transformation studies of iron oxide nanoparticles

Abstract

The effect of isochronal annealing on the phase transformation in iron oxide nanoparticles is reported in this work. Iron oxide nanoparticles were successfully synthesized using an ash supported technique followed by annealing for 2 h at various temperatures between 300 and 700 • C. It was observed using X-ray diffraction (XRD) and transmission electron microscopy (TEM) that as-grown samples have mixed phases of crystalline haematite (α-Fe 2 O 3 ) and a minor phase of either maghemite (γ-Fe 2 O 3 ) or magnetite (Fe 3 O 4 ). On annealing, the minor phase transforms gradually to haematite. The phase transformation is complete at annealing temperature of 442 • C as confirmed by differential scanning calorimetric (DSC) analysis. The unresolved phases in XRD were further analysed and confirmed to be maghemite from the X-ray absorption near edge structure (XANES) studies. The magnetic measurements showed that at room temperature nano-α-Fe 2 O 3 is weak ferromagnetic, and its magnetization is larger than the bulk value. The mixed phase sample shows higher value of magnetization because of the presence of ferromagnetic γ-Fe 2 O 3 phase.

Correlation between Particle Size, Strain and Band Gap of Iron Oxide Nanoparticles

“…The iron oxide nanoparticles were obtained in the form of residue [9]. These iron oxide nanoparticles are designated as, As Prepared sample (sample #1).…”

“…1. are due to γ-Fe 2 O 3 (JCPDS 15-0615) phase [9] Intensities of these peaks (marked A in figure 1) are much smaller than the major peaks and therefore, these peaks are from a minor phase. The peaks marked as B are assigned to α-Fe 2 O 3 phase (JCPDS # 24-0072) having rhombohedral symmetry (space group: R-3 [148]).These peaks are from the major phase.…”

“…Beyond annealing temperature of 400° C, peaks A completely disappear and only peaks corresponding to phase B remain. Particle size and strain of the nanoparticles was calculated using Williamson hall plot [9]. In Fig.…”

Utilization of Fe2O3 Nanoparticles Synthesized by Novel ASH Supported Method in Arsenic Adsorption from the Contaminated Water

“…It can also be attributed due to an increase in the energy bandgap and a decrease in the strain of iron oxide nanoparticles. [ 19,21 ]…”

“…In the present study, inorganic Fe 2 O 3 nanoparticles are employed, which are prepared from the novel ASH SUPPORTED method [ 19 ] utilized first time for the removal of arsenic from the contaminated water. Although, there are numerous methods to prepare iron oxide nanoparticles, which are rigorous, expensive, and are not environmentally friendly.…”