The structural changes of MnO2, Fe2O3 and graphite under separate and joint mechanical activation in high-energy planetary ball mill were studied by X-ray diffraction analysis, Raman spectroscopy and chemical analysis. Separate mechanical processing resulted in nanostructured states of MnO2, Fe2O3 and graphite with the size of coherent scattering regions of 25, 12 and 6 nm, respectively, and the average particle size of 15-20 nm. Along with nanoparticles of globular shape, Fe2O3 nanorods were found to be formed during separate milling. No mechanochemical effect was found after separate milling. Under joint mechanical activation of nanostructured manganese and iron oxides with graphite, phase transformations toward less stable forms of oxides (Mn2O3, Mn3O4, Fe3O4) were found. When co-milled with a-Fe2O3, graphite was found to exfoliate to graphene layers. The graphite phase remained under the combined mechanical activation with MnO2. Dynamic recrystallization of alpha-Fe2O3 phase also proceeded during joint mechanical activation of nanostructured Fe2O3 and graphite. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.