A Hydrothermal-Calcination Process with Ammonium Dihydrogen Phosphate as Restricted Growth Agent for the Fabrication of Magnetic Fe3O4/α-Fe2O3 Heterogeneous Nanosheets

A facile hydrothermal-calcination process was employed to fabricate Fe3O4/alpha-Fe2O3 heterogeneous nanosheets utilizing NH4H2PO4 as the restricted growth agent and FeCl3 as the iron source. The morphologies and properties of the obtained nanomaterials were investigated by SEM, XRD, VSM, and TEM techniques. In the hydrothermal process, an H2PO4- concentration of 1.44 mM, Fe3+ concentration of 20 mM, a hydrothermal temperature of 220 degrees C, and a hydrothermal time of 24 h were selected as the optimal conditions for alpha-Fe2O3 nanosheets, their average diameter and thickness of the resulting nanosheets were approximately 150 and 53 nm. Subsequently, glucose was utilized as a reducing agent to partially reduce the precursor of alpha-Fe2O3 to Fe3O4, thereby forming Fe3O4/alpha-Fe2O3 heterogeneous nanosheets. During the calcination process, the effects of calcination time, calcination temperature, and glucose content on the morphology and properties of the nanosheets were investigated. The morphology and size of the prepared nanosheets did not change significantly during the calcination process, while the magnetic properties of the products underwent significant changes. When the product was calcined at 600 degrees C for 4 h with a mass ratio of precursor to glucose was 1:12, the saturation magnetization of as-prepared Fe3O4/alpha-Fe2O3 heterogeneous nanosheets reached the largest of 80 emu/g. The results indicated that the Fe3O4/alpha-Fe2O3 heterogeneous nanosheets with satisfactory saturation magnetization were successfully fabricated with glucose as the reductant.