FERRITE FORMATION IN AQUEOUS-SOLUTION AT 100-200-DEGREES-C

The formation of Fe3O4 and Ni(II)-ferrite films by oxidation of Fe(II) in aqueous solution was studied in the temperature range 100-200°C. To make it possible to perform the study, a special piece of equipment was designed with two high-pressure pumps, which could introduce the aqueous solutions of Fe(II) ions and the oxidizing agent (NaNO2) into a reaction cell at a high pressure (105-2 × 106 Pa). Fe3O4 was obtained below 120°C for pH above 5.5, but two products of Fe3O4 and α-Fe2O3 were obtained above 120°C. For the reaction solution containing Fe(II) and Ni(II) ions, only the Ni(II)-ferrites appeared in the temperature range 100-200°C, where the two products of Fe3O4 and α-Fe2O3 appeared for the reaction solution containing only the Fe(II) ion. The Ni(II) content in the Ni(II)-ferrite increased with an increase in Ni(II) concentration in the reaction solution and/or with temperature. © 1990.