RAFAEL GITTI TORTORETTO FIM

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    Artigo IPEN-doc 25915
    Influence of alloying elements Zr, Nb and Mo on the microstructure and magnetic properties of sintered Pr-Fe-Co-B based permanent magnets
    2018 - SILVA, M.R.M.; FIM, R.G.T.; SILVA, S.C.; CASINI, J.C.S.; WENDHAUSEN, P.A.P.; TAKIISHI, H.
    The addition of alloying elements on rare-earth permanent magnets is one of the methods used to improve the magnetic properties. This present work evaluates the influence of alloying elements such as Zr, Nb and Mo on the microstructure and magnetic properties of sintered Pr-FeCo- B based permanent magnets. The permanent magnets were produced by the conventional powder metallurgy route using powder obtained by hydrogen-decrepitation (HD) method from as cast alloys. In order to produce the magnet Pr16Fe66,9Co10,7B5,7Cu0,7 without alloying elements the mixture of alloys method was employed, mixing two compositions: Pr20Fe73B5Cu2 (33% w.t) and Pr14Fe64Co16B6 (67% w.t). With the purpose of evaluating the influence of the alloying elements, the Pr14Fe64Co16B6X0,1 (where X= Zr, Nb or Mo) (67% w.t) alloy was employed. The characterization of the alloys and the magnets was carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS) and the magnetic properties were measured using a permeameter. The magnet without any additions presented the highest intrinsic coercivity (ļ­0iHc = 748 KA.m-1) while the magnet with Nb addition presented higher remanence (Br = 1,04 T). The magnet with Zr addition presented the highest maximum energy product (BHmĆ”x = 144 KJ.m-3), and the magnet with Mo addition showed the highest squareness factor (SF = 0,73).
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    Artigo IPEN-doc 25914
    Influence of milling time on magnetic properties and microstructure of sintered Nd-Fe-B based permanent magnets
    2018 - FIM, R.G.T.; SILVA, M.R.M.; SILVA, S.C.; CASINI, J.C.S.; WENDHAUSEN, P.A.P.; TAKIISHI, H.
    In this paper, the effect of the grain size on sintered Nd-Fe-B based permanent magnets was investigated. In order, the magnets were produced by different milling times at 200 rpm and then vacuum sintered at 1373 K for 60 minutes followed by cooling outside the furnace. The magnets either produced by lower and higher milling times (30 and 75 minutes) exhibited lower remanence and coercivity, due the inhomogeneous distribution of the grain sizes. The magnet produced by intermediary milling time (45 minutes) exhibited the highest properties among all samples, with remanence of 1.06 T, coercivity of 891.3 KA.m-1, maximum energy product of 211 KJ.m3 and a squareness factor equal 0.92.