In situ ultra-small-angle X-ray scattering study of the solution-mediated formation and growth of nanocrystalline ceria

Results are presented for an in situ synchrotron-based ultra-small-angle X-ray scattering (USAXS) study of the solution-mediated formation and growth of nanocrystalline ceria (n-CeO(2)) using a new remote-controlled, isothermal, circulating fluid flow cell. The fluid flow mitigates or reduces X- ray beam-induced damage, air bubbles or particulate flocculation within the bulk solution, but prevents any coarse particulates that do form from settling out from suspension. Combined with the large-scale range accessible in USAXS studies, the flow cell has enabled measurement, in situ and in real time, of structural characteristics from 10 angstrom to a few micrometres in size as a function of the changing physical and chemical conditions. By applying a multi-component model, the nanoparticle formation and growth component has been identified. Control and online monitoring of flow rate, temperature and pH suspension conditions have permitted real-time studies of the formation and growth of the individual n-CeO(2) particles from homogeneous dilute solution over several hours. Aspects of the nanoparticle nucleation and growth are revealed that have not been observed directly in measurements on this system. (c) 2008 International Union of Crystallography Printed in Singapore - all rights reserved.