In Situ Ultra-Small-Angle X-Ray Scattering Study of the Solution-Mediated Formation and Growth of Nanocrystalline Ceria
Andrew J. Allen, Vincent A. Hackley, P R. Jemian, Jan Ilavsky, J M. Raitano, S W. Chan
A remote-controlled isothermal circulating fluid flow cell is described and results presented for the in situ ultra-small-angle x-ray scattering (USAXS) study of solution-mediated systems and suspensions. The fluid flow prevents settling out of coarse particulates from suspension. Control and online monitoring of flow rate, temperature and suspension conditions such as pH permit real-time studies of solution-mediated processes over several hours. By flowing liquid samples, x-ray induced damage to soft materials and the generation of air bubbles can be reduced or eliminated. Used in conjunction with the large nanometer-to-micrometer scale range accessible in USAXS studies, the flow cell can meausre, in situ and in real time, nanoscale--to-microscale structural characteristics as a function of changing physical and chemical conditions. First results for a real-time flow cell study of nanocrystalline ceria precipitation from solution are presented. Previously unobserved aspects of nucleation and growth in the nanoparticulate ceria formation are revealed. Potential applications for flow cell studies of solution-mediated processes, carbon nanotube systems and bio-particle ensembles are briefly summarized.