Structural investigation of Fe2O3-SiO2 nanocomposites through radial distribution functions analysis

Two Fe2O3-SiO2 nanocomposites containing 50% by weight of iron oxide were prepared by a sol-gel method. By changing the surface to volume ratio of the gelling mass from 0.04 (sample A) to 0.3 cm(-1) (sample B), gelation times changed, resulting in nanoparticles of average size of about 10 and 4 nm, respectively. Accurate X-ray diffraction (XRD) data were collected and used to calculate total structure and correlation functions. The analysis of these functions unequivocally proved that in both samples maghemite is the iron oxide formed. The result demonstrated that decreasing the gelation time gives rise to the formation of smaller and smaller nanoparticles of the same phase. The possibility of interpreting the XRD pattern of sample B in terms of occurrence of 2-line ferrihydrite was discussed.