Magnetic Phase Development of Iron Oxide-SiO2 Aerogel and Xerogel Prepared using Rice Husk Ash as Precursor

This study is aimed to produce iron incorporated silica aerogel and xerogel from rice husk ash. Two sol--gel chemistry routes have been used to synthesize both samples. Iron in the form of hydrated iron nitrate with compositions in the range of 3-17 wt%(Fe2O3/Fe2O3+SiO2) were used as iron source. For aerogel samples, iron was added at the solution level whereas for xerogel samples, iron was added after the gelation. The synthesis of iron doped aerogel was done by supercritical drying at temperature about 250 deg. C and pressure of about 5.9 MPa (850 psi) while xerogel was formed by drying the aquagel in an oven at 110 deg. C for 24 hours. The iron doped aerogel and xerogel composites were further heated to various temperatures to obtain the magnetic phase. Results show that the only sample that signifies the presence of maghemite (γ-Fe2O3) is the aerogel sample doped with 7.3 wt% iron at temperature 1100 deg. C while other samples show the presence of magnetite.