SYNTHESIS AND CHARACTERIZATION OF CHROMIUM AND MANGANESE OXIDES

Abstract

In the present dissertation different oxides of chromium and manganese were prepared by the hydrolysis of their respective metal nitrates with sodium hydroxide by precipitation method. The precursor and the oxides were characterized by various analytical techniques such as TG-DTA, Powder XRD. FE-SEM, EDAX. TGA studies for chromium oxide showed a phase transition at 224°C and for manganese oxide showed the existence of different forms at different temperature. The XRD suggests that the chromium oxide formed is CrO, which changes to Cr203 when heated to 500°C either in H2 or N2 atmosphere but with different lattice parameters. Manganese hydroxide formed changes to Mn,03 when heated at 750°C in air whereas it changes to Mn304 when heated at 500°C in N2 atmosphere for 8 hours. In FE-SEM images the particles look agglomerated with irregular morphology