Ferrite formation in aqueous solution at 100–200°C

Abstract

The formation of Fe 3O 4 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 (NaNO 2) into a reaction cell at a high pressure (10 5−2 × 10 6 Pa). Fe 3O 4 was obtained below 120°C for pH above 5.5, but two products of Fe 3O 4 and α-Fe 2O 3 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 Fe 3O 4 and α-Fe 2O 3 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.