JONHSON DELIBERO ANGELO

JONHSON DELIBERO ANGELO

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The effect of niobium and boron content on magnetic properties and corrosion resistance of Pr-Fe-Co-B-Nd HD magnets
2007 - ANGELO, J.D.; MOTTA, C.C.; BARBOSA, L.P.; TAKIISHI, H.; COSTA, I.; FARIA, R.N.
The influence of cobalt content on the magnetic properties and corrosion of PrFeCoCuNbB sintered magnets
2004 - ANGELO, J.D.; TAKIISHI, H.; COSTA, I.; FARIA JUNIOR, R.N.; MOTTA, C.C.
The effect of aeration on the corrosion process of magnetized Nd-Fe-B magnets
2004 - OLIVEIRA, M.C.L.; FARIA JUNIOR, R.N.; ANGELO, J.D.; COSTA, I.; MELO, H.G.
The effects of aeration upon the corrosion process of magnetized Nd-Fe-B based sintered magnets have been studied. The tests were carried out in naturally aerated and in deaerated 3.5 (wt.%) sodium chloride solutions at various testing times by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. In deaerated solution the magnets exhibit higher impedance values (one order of magnitude) than in aerated one. Bode phase angle diagrams obtained in the former solution presented a single broad time constant, indicating the existence of a single process in the investigated frequency range; moreover, the impedance behaviour was maintained fairly constant from 5 days of immersion throughout the rest of the testing period. On the other hand, the sample immersed in the aerated solution presented a constant and slow diminution of the impedance all long the immersion time. In this case, Bode phase angle diagrams presented a HF shoulder interpreted as the influence of the magnetic field on the transport of oxygen to the interface. Larger icorr values and more noble potentials were also obtained for the magnet in aerated solution. In the presence of oxygen, the corrosive attack penetrated deeply into the specimens and, consequently, the magnetic properties diminished with immersion time. The magnetic properties most influenced by corrosion were the remanence (Br) and the maximum energy product (BHmax).
The effect of particle size distribution on the magnetic properties of Pr-Fe-B sintered magnets
2003 - ANGELO, J.D.; PERIGO, E.A.; MOTTA, C.C.; FARIA JUNIOR, R.N.
This paper reports the results of investigations carried out to determine the influence of the particle size distribution on the magnetic properties of Pr16Fe76B8sintered magnets. Permanent magnets were prepared from the cast alloy using the powder metallurgy route and the hydrogen decrepitation process. The effect of the balls shape and weight on the particle size distribution was investigated. Spherical milling balls yielded magnetic powder with a single particle size distribution whereas spherical/tori balls yielded hydride powder with a bimodal particle size distribution.
Estudo das propriedades e microestrutura de ímãs permanentes de terras raras e metais de transição preparados pelo processo de decrepitação hidrogênio
2005 - ANGELO, JOHNSON D.
The effect of niobium and boron content on magnetic properties and corrosion resistance of Pr-Fe-Co-B-Nb HD magnets
2008 - ANGELO, J.D.; MOTTA, C.C.; BARBOSA, L.P.; TAKIISHI, H.; COSTA, I.; FARIA, R.N.
The hydrogenation decrepitation process was employed to produce sintered magnets using a mixture of two alloys. The effect of niobium and boron content on the magnetic properties of Pr14FebalCo16BxNby-type sintered magnets was studied. Niobium and boron have a significant effect on the magnetic behavior of these permanent magnets. The optimum amount of boron was 6 at% and niobium should be kept below to 0.50 at%. The squareness factor (0.90) has been improved considerably and good overall magnetic properties (Br=1320 mT, iHc=700 kAm-1 and (BH)max=315 kJm-3) have been achieved for the sintered magnets prepared from the Pr14Fe63.85Co16B6Nb0.15 alloy.