Small-angle x-ray scattering studies of early-stage colloid formation by thermohydrolytic polymerization of aqueous zirconyl salt solutions

Early-stage processes involving the polymerization of zirconium species in aqueous solutions at elevated temperatures (similar to 100 degrees C) as we ll as colloid formation were studied. Small-angle x-ray scattering (SAXS) d ata were analyzed via Guinier, "longrods," and Pored plots to determine par ticle growth kinetics and morphology. Our SAXS data suggest that zirconium tetramers and octamers polymerize into larger clusters and elongated-rod-(o r needle)-shaped primary particles, which have a length of a few nanometers and a radius of gyration of cross section between 4 and 5 Angstrom. Cube-s haped particles are aggregates of the needlelike primary particles. The tra nsition from zirconium tetramer to a colloidal sol particle follows a mass- fractal growth (1 < fractal dimension, D < 3).