Preparation of nanoparticles and hollow spheres of α-Fe2O3 and their properties

Abstract

Uniform nanoparticles and hollow microspheres of hematite (a-Fe 2 O 3 ) were obtained via a hydrothermal method by using iron (III) chloride as a precursor. The effects of reactant concentration, reaction time and temperature on the morphology of the samples were studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and superconducting quantum interference device magnetometer (SQUID) measurement. a-Fe 2 O 3 nanoparticles show a superparamagnetic behavior and the average size of the spherical particles was around 60 nm. However, hollow microspheres show a normal ferromagnetic behavior at room temperature with remanent magnetization and coercivity of 0.2482 emu/g and 2,516 Oe, respectively, and their average diameter was around 2 lm. The effects of reactant concentration and reaction temperature on the formation of the products were investigated. The experimental results reveal that the magnetic properties of hematite can be tuned by controlling the morphology.

Synthesis, morphology, microstructure and magnetic properties of hematite submicron particles

“…The existence of the hysteresis loop below T M (AF region) shows that uncompensated spins exist at the surface of particles. The influence of the shape and microstructure of the particles on the coercivity is well known and an increase of the coercivity with increasing aspect ratio has been reported [26][27][28][29][30][31][32][33][34][39][40][41][42][43]47,55,78]. For example, in nanosized Fe, increases of aspect ratio by a factor 5 (from one to five) increases coercivity ten times [78].…”

“…Among these techniques, hydrothermal is one of the most reliable and effective synthesis methods. The morphology and crystallinity in hydrothermal process can be controlled by varying parameters such as pressure, temperature, reaction time, solution pH value, reactant concentration, solvent, surfactant and precursor [1,10,16,19,21,26,28,31,[39][40][41][42]61,62,[64][65][66][67][68]. This technique provides relatively low process temperature and reduces processing time.…”

“…This technique provides relatively low process temperature and reduces processing time. Various morphologies of ␣-Fe 2 O 3 such as stalactite-like, coral-like, cluster-like, cube, porous, snowflake-like, star-like, ringlike, urchin-like, hexagonal, nanotubes, nanoplatelets, nanorods, flower-like, nanospheres, nanoaggregates and nanorhombohedra with a wide range of the magnetic properties have been reported showing huge possibilities of the hydrothermal method [1,10,16,19,28,31,38,39,42,43,[61][62][63][64][65][66][67][68][69][70][71]. However, only a few reports involve the formation of ␣-Fe 2 O 3 plate-like structures [59,[70][71][72][73][74][75].…”