Equimolar mixtures of graphene and iron oxide nanoparticles were subjected to mechanochemical activation. The phase sequence was investigated using Mӧssbauer spectroscopy as function of ball milling time. For low milling times (2-4 hours) the series with hematite (Fe2O3) nanoparticles was fitted with 2 sextets, corresponding to hematite with carbon introduced in the lattice. At high milling times (8-12 hours) the same series exhibited an additional sextet with hyperfine parameters characteristic to iron carbides and a quadrupole-split doublet, which could be assigned to carbon clusters with small amounts of iron in them. The series with magnetite nanoparticles (Fe3O4) at low milling times was analyzed considering 2 sextets, corresponding to the tetrahedral and octahedral sites of magnetite. At high milling times, the magnetite series also exhibited a broad sextet representing iron carbides and the doublet associated with iron-containing carbon clusters. Supporting information was obtained by determinations of the recoilless fraction. The results were compared with those obtained by ball milling graphite with hematite and magnetite nanoparticles.

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