Nanocrystalline Maghemite {(γ-Fe{\textless}sub{\textgreater}2{\textless}/sub{\textgreater}O{\textless}sub{\textgreater}3{\textless}/sub{\textgreater})} in Silica by Mechanical Activation of Precursors

Abstract

{03B3-Fe2O3} nanocrystallites dispersed in an amorphous silica matrix have been successfully prepared for the first time by mechanical activation of a chemistry-derived precursor at room temperature. The initial 10 h of mechanical activation triggered the formation of nanocrystallites of {Fe3O4} in a highly activated matrix. Increasing the mechanical-activation time led to a phase transformation from {Fe3O4} to {03B3-Fe2O3.} The {03B3-Fe2O3} phase was well established after mechanical activation of the precursor for 30 h. Further increasing the mechanical-activation time to 40 h induced the formation of {03B1-Fe2O3.} The mechanical-activation-grown {03B3-Fe2O3} nanocrystallites were {223C10201312} nm in size and well dispersed in the silica matrix, as observed using {TEM.} They demonstrated superparamagnetic behavior at room temperature when measured using a Mössbauer spectrometer and a vibrating sample magnetometer {(VSM).} In addition, the {03B3-Fe2O3} derived from 30 h of mechanical activation exhibited a value of saturation magnetization as high as 62.6 emu/g.