EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Rare Earths (RE) have the prospect of being used in clean technologies, such as, for example, wind turbines and hybrid vehicles, in addition to strategic segments in communication and oil, which are limited by rare earth availability. The disadvantage of rare earth processing is related to rapid oxidation and higher reactivity of transition metals. In that case, (RE)-based powders must be produced and handled in a controlled atmosphere, which increases processing cost. On the other hand, nanostructured materials have a huge surface and can be used for control to prevent rare earth oxidation. The aim of this work was to study the mechanical milling of (RE)-based powders with reduced graphene oxide (rGO). rGO was obtained by a thermal reduction after the synthesis of graphene oxide (GO) by a modified Hummers method. Rare-earth-based powders were produced by a hydrogen-decrepitation process before mechanical milling. GO and rGO were characterized by X-ray diffraction. The XRD pattern of GO displayed a peak at 2θ ≈ 12°. After heat treatment and thermal reduction, the peak was shifted to 2θ ≈ 24°, showing that the thermal reduction process decreases the interplanar spacing. Moreover, mechanically milled powders were analyzed by Transmission Electron Microscopy that showed RE-based powders were covered by rGO. The average particle size was 2-5 mm with milling times in the range of 7 to 45 min determined by the Fisher-Sub Sieve Size method. Characteristic X-ray photoelectron spectroscopy spectra for the rGO and (RErGO)-based powders were obtained in the C1s, O1s, Co2p, Fe2p, and Nd3d regions. XPS spectra show an interaction between (RE)-based powders and rGO. Besides that, rGO acted as a lubricant, antioxidant, non-binding agent, avoiding the welding of particles in the milling bowl.