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Synthesis and microstructural characterisation of manganese oxide nanoparticles

In a previous work, the morphologies of γ-Fe2O3 particles were modified by addition of divalent metal cations. Divalent metal cations gradually modified the γ-Fe2O3 spindles to pseudosphere and the nanotube to nanoring particle morphologies. The modification with divalent metal cations (Mn2+, Cu2+, Zn2+ or Ni2+) initiated the changes in morphology of γ-Fe2O3 particles, but had no influence on chemical composition of γ-Fe2O3 particles. These are because upon exposure to the hydrothermal and acidic conditions (pH ≤ 2) divalent metal cations do not precipitate or adsorb on the γ-Fe2O3 particles and also, there is no oxidation divalent cations. In this work, spherical Mn3O4 nanoparticles and γ-MnOOH and MnO2 nanoparticles of 1D morphology were hydrothermally synthesised and microstructurally characterised using Electron Microscopy, FT-IR and XRD analyses. The hydrothermal synthesis of MnO2 started from KMnO4 precursor. Quite opposite to γ-Fe2O3 system, introduction of Mn2+ cation in the system caused a series of oxidation/reduction reaction that had remarkably influence not only on the morphology, but also the phase composition of formed MnO2 nanoparticles. The mechanism, structure and morphology of manganese oxide nanoparticles generated in hydrothermal syntheses are discussed.

manganese oxide; nanoparticles; nanorods; nanotubes; hydrothermal synthesis; Mn2+ cation

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