Synthesis of MnNiP2O7 and nonisothermal decomposition kinetics of a new binary Mn0.5Ni0.5HPO4 · H2O precursor obtained from a rapid coprecipitation at ambient temperature

Abstract

The new binary metal hydrogen phosphate monohydrate Mn05Ni 0.5HPO4 · H2O was synthesized by a rapid and simple coprecipitation method using phosphoric acid, manganese metal, and nickel carbonate at ambient temperature. The kinetics of dehydration of Mn 05Ni0.5HPO4 · H2O was studied under nonisothermal heating by thermogravimetry (TG), and its final decomposition product was a binary metal pyrophosphate, MnNiP2O 7. The activation energies of the dehydration step of Mn 05Ni0.5HPO4·H2O were calculated through the isoconversional methods of Ozawa and Kissinger-Akahira- Sunose (KAS), and the possible conversion functions have been estimated through the Coats-Redfern method. The activation energies calculated for the dehydration of Mn05Ni0.5HPO4 · H2O by different methods and techniques were found to be consistent. The possible conversion function of the dehydration reaction for Mn05Ni 0.5HPO4 · H2O was "spherical symmetry" of a "three-dimensional diffusion mechanism". © 2008 American Chemical Society.