ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Uniform particles of controlled morphology of CeOSO4·H2O may be prepared by forced hydrolysis, at 90 °C, of solutions of cerium (IV) sulphate. A structural description is given here of the different steps of the forced hydrolysis before precipitation takes place. It uses essentially the complementary techniques of extended X-ray absorption fine structure spectroscopy and small-angle X-ray scattering to characterize, at different length scales, the structural evolution of the solution. The first step, which occurs as temperature is raised above 60 °C, is an inorganic polymerization that transforms molecular dimeric precursors Ce2(OH)2O12 into colloidal particles. In the second step, at the ageing temperature of 90 °C, no chemical and structural changes are revealed; the solution has reached an equilibrium state characterized by the presence of 3 nm large monodisperse colloids which use 85% of the initial cerium ions and smaller particles (15%). The detailed local structure around the cerium atoms in the colloids is compatible with the formation of a chain-like structure of Ce(IV) ions via hydroxo bridges (Ce(OH)2) n 2n+ . A mechanism to explain the transformation of precursors into colloids is proposed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00361172
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