Non-isothermal decomposition of NiC 2O 4–FeC 2O 4 mixture aiming at the production of NiFe 2O 4

Abstract

The non-isothermal decomposition of NiC 2O 4·2H 2O–FeC 2O 4·2H 2O (1:2 mole ratio) mixture was studied on heating to the formation of NiO–Fe 2O 3 mixture at 350 °C in air atmosphere using thermogravimetry. Kinetic analysis of data according to the integral composite method showed that the oxidative decomposition of FeC 2O 4 and NiC 2O 4 are best described by the three-dimensional phase boundary model. The activation parameters were calculated and discussed. The solid products at different decomposition stages were identified using XRD, Mössbauer and FT-IR spectroscopic techniques. Some characteristic XRD lines of NiFe 2O 4 start to appear at 800 °C beside the characteristic lines of NiO and Fe 2O 3, whereas at 1000 °C, only the characteristic lines of single phase cubic NiFe 2O 4 appeared. The Mössbauer spectrum at 1000 °C fitted into two Zeeman sextets characteristic of Fe 3+ on the tetrahedral (A) and octahedral (B) sites of NiFe 2O 4 inverse spinel. Consistent results were obtained using FT-IR where the absorption bands appeared at 602 and 407 cm −1 for the mixture calcined at 1000 °C. These can be assigned to the intrinsic vibrations of tetrahedral and octahedral sites of NiFe 2O 4, respectively.