Preparation of Well Defined Colloidal Particles by Thermal Decomposition of Metal Chelates II. Cobalt and Nickel

Metal and metal oxide precipitates exhibiting different morphologies were prepared by hydrothermal aging of strongly alkaline solutions of chelated nickel (II) or cobalt (II) salts at 250 C. Triethanolamine (TEA) (ethylenedinitrilo)tetraacetic acid (EDTA), and N-(2-hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA) were found to be suitable chelating agents. The oxidation state of the metal in the final product was controlled by the addition of either hydrazine (N₂H₄) or hydrogen peroxide (H₂O₂) to the reaction mixture. In some instances, particle size and morphology were affected by the concentration and type of anions present in the precipitation medium. The importance of such chelate decomposition studies to the development of suitable chemical decontamination formulations for the primary coolant circuits of nuclear reactors is discussed. In addition, the uniform solids may be of practical interest in a variety of technological areas.