Produção e caracterização de nanoplacas metálicas obtidas por moagem de alta-energia

Abstract

Monometallic and bimetallic nanoplates were prepared by high energy wet milling from elemental metal powders or from mixtures of powders combined in pairs of the M - Fe (M = Transition Metal) type. Structural analyzes and of the hyperfine and magnetic properties revealed that the thickness of the nanoplates produced for a fixed set of milling conditions in a ball mill depends specifically on the metal processed. However, always have follicular or circular form, with thicknesses below 100 nm. For iron, it was found that the orientation of the magnetic domains lies preferentially in the plane of nanoplates. The bimetallic systems investigated are structured so that iron is encrusted in the M metal, but is not mixed at atomic scale. This is attributed to the "process control agents" - i.e., lubricants and surfactants - that characterize the milling as "wet" and avoid mechanosynthesis. In particular, the iron nanoplates were coated with a frozen aqueous solution of acetate-M, freeze-dried and, further, annealed in a hydrogen atmosphere. It was observed that, depending on M, the iron nanoplates turn into M or M-oxide bearing, or, even, react to form solid solutions and intermetallic compounds. All these results are discussed on basis of potential technological applications of the nanoplates produced.