Structure and thermal properties of iron (III) hydroxide xerogels obtained under high intensity ultrasonic treatment were studied by means of small-angle neutron scattering and heat-flux calorimetry. It was established that sonication affects the mesostructure of amorphous xerogels (i.e., increase in their homogeneity, surface fractal dimension, and the sizes of aggregates of primary particles) as opposed to the commonly accepted point of view that ultrasonic action cannot lead to notable changes in structure of powders, consisting of nanometer size particles. Ultrasonically induced structural changes in xerogels are evidently confirmed via their notably different reactivity at thermal decomposition under hydrothermal conditions.

• Received 3 April 2008

DOI:https://doi.org/10.1103/PhysRevB.81.174201