Non-isothermal decomposition of NiC2O4-FeC2O4 mixture aiming at the production of NiFe2O4

The non-isothermal decomposition of NiC2O4.2H(2)O.FeC2O4.2H(2)O (1:2 mole ratio) mixture was studied on heating to the formation of NiO-Fe2O3 mixture at 350 T in air atmosphere using thermogravimetry. Kinetic analysis of data according to the integral composite method showed that the oxidative decomposition of FeC2O4 and NiC2O4 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, Mossbauer and FT-IR spectroscopic techniques. Some characteristic XRD lines of NiFe2O4 start to appear at 800 T beside the characteristic lines of NiO and Fe2O3, whereas at 1000 degreesC, only the characteristic lines of single phase cubic NiFe2O4 appeared. The Mossbauer spectrum at 1000 T fitted into two Zeeman sextets characteristic of Fe3+ on the tetrahedral (A) and octahedral (B) sites of NiFe2O4 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 degreesC. These can be assigned to the intrinsic vibrations of tetrahedral and octahedral sites of NiFe2O4, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.