Hydrothermal synthesis of beta-FeO(OH) rod-like particles with uniform size distribution

beta-FeO(OH) particles were prepared by a two-step hydrothermal precipitati on. First, the hydrolysis of 0.25 mol dm(-3) FeCl3 acidic solution at 90 de grees C produced beta-FeO(OH) fine seed crystallites. Next, an appropriate amount of urea was added to the beta-FeO(OH) acidic suspension, then heated to the pre-determined temperature for further hydrolytic precipitation. Th e effects of the [(NH2)(2)CO]/[Fe3+] molar ratio and the hydrothermal tempe rature on both the precipitation rate and the particle size were studied. T he precipitation rate increased with the [(NH2)(2)CO]/[Fe3+] molar ratio an d with the hydrothermal temperature, and a simple model for the hydrolysis reaction was supposed on these experimental results. The particle size of b eta-FeO(OH) precipitates was almost independent of both the molar ratio and the hydrothermal temperature, and their particle size distribution was rel atively narrow. It was thought to be attributed to the separation between t he nucleation and the particle growth via the two-step hydrolysis reaction. In addition, it was found that the remaining chloride amount in the obtain ed beta-FeO(OH) precipitates were remarkably low. (C) 2000 Elsevier Science B.V. All rights reserved.