Phase Transformation of Iron Oxide Nanoparticles from Hematite to Maghemite in Presence of Polyethylene Glycol: Application as Corrosion Resistant Nanoparticle Paints

This work proposes a simple method for the efficient and rapid synthesis of hematite (α-Fe2O3) nanostructures based on simple heating method under ambient conditions. Polyethylene glycol (PEG) is employed as a structure directing agent in driving the morphology and phase transformation. Typically, Fe2O3 nanoparticles of size below 50 nm were synthesized at temperature around 500°C. The morphology and mechanism of formation of the nanocapsules and then aggregation of nanocapsules to form larger size nanoclusters were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy. Interestingly, this work demonstrates the structural phase transformation of hematite (α-Fe2O3) to maghemite (γ-Fe2O3) upon addition of different amounts of PEG (say 0.066 M, 0.133 M, and 0.2 M) and then heat treating at 500°C. The prepared powders were used in nanoparticle paint preparation and applied as corrosion resistant coatings on iron samples. Polarization studies performed on the paint coatings made out of all the prepared samples showed size-dependent corrosion resistance. As the particle size decreases, the surface area increases and so the corrosion resistance also increases.