Structure and morphology evolution of hematite (α-Fe2O3) nanoparticles in forced hydrolysis of ferric chloride

Hematite (alpha-Fe2O3) nanoparticles were prepared by forced hydrolysis of ferric chloride under acidic pH conditions. Without introduction of any additives, hematite nanoparticles with varying sizes and morphologies were obtained by controlling the nucleation rate, Fe3+ concentration, and aging time. Synthesized primary nanocrystals show such morphologies as cubic, spherical, sheetlike, and hexagonal structures and unusual disklike and tetrahedral aggregates. In addition to previous findings that phase transformation usually occurs from akaganeite (beta-FeOOH) to hematite during forced hydrolysis, direct transformation of amorphous iron oxides to crystalline hematite at an early stage of hydrolysis were also observed and confirmed by X-ray diffraction and Raman spectroscopic analysis.