Reprocessing of commercial REFeB (RE = Nd or Pr) sintered magnets for preparation of bonded magnets and semi-hard magnetic compounds using hydrogen

• Grant number: 10/08018-8
• Support type: Scholarships in Brazil - Post-Doctorate
• Effective date (Start): August 01, 2010
• Effective date (End): June 30, 2012
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Transformation Metallurgy
• Principal Investigator: Fernando Jose Gomes Landgraf
• Grantee: Élio Alberto Périgo
• Home Institution: Instituto de Pesquisas Tecnológicas S/A (IPT). Secretaria de Desenvolvimento Econômico (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

In this work a study concerning the reprocessing of sintered REFeB (RE = Nd and/or Pr) magnets to prepare bonded magets and semi-hard magnetic compounds will be carried out. Firstly, REFeB powders with optimized remanence and coercivity are intended to be obtained by means of hydrogen decrepitation and/or the hydrogenation-disproportionation-dessorption-recombination processes. Processing conditions as the exposure time and hydrogen dessorption temperature will be verified. The magnets will be prepared by uniaxial pressing. Besides, the aging of powders will be verified in distinct conditions under air. Due to their intrinsic properties, the hydrides Nd2Fe14BHx and/or Pr2Fe14BHx will be studied as potential semi-hard magnetic materials. Both of them have magnetization comparable to that of Fe50Ni50 (~155 Am2kg-1) and reduced magnetocrystalline anisotropy. The latter makes possible a low coercivity compared to that of the RE2Fe14B phase. The processes of hydrogen absorption will be used and studied in a similar way compared to the first case. Magnetic characterization will be carried out by a vibrating sample magnetometer (powder) and hysteresisgraph (magnet). Microstructural characterization will be performed by SEM, TEM, XRD and TMA. Further techniques may also be employed depending of the project results. (AU)

Scientific publications

(4)

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

PERIGO, E. A.; CRUZ, I. A.; ANTUNES, B.; BRAGA, A. P. V.; LANDGRAF, F. J. G. How Extrinsic Is the Coercivity in NdFeB Bonded Magnets?. IEEE Transactions on Magnetics, v. 49, n. 9, p. 5043-5047, SEP 2013. Web of Science Citations: 3.

PERIGO, E. A.; DE CAMPOS, M. F.; FARIA, R. N.; LANDGRAF, F. J. G. The effects of the pressing step on the microstructure and aging of NdFeB bonded magnets. Powder Technology, v. 224, p. 291-296, JUL 2012. Web of Science Citations: 10.

PERIGO, E. A.; SILVA, S. C.; DE SOUSA, E. M. B.; FREITAS, A. A.; COHEN, R.; NAGAMINE, L. C. C. M.; TAKIISHI, H.; LANDGRAF, F. J. G. Properties of nanoparticles prepared from NdFeB-based compound for magnetic hyperthermia application. Nanotechnology, v. 23, n. 17 MAY 4 2012. Web of Science Citations: 10.

PERIGO, E. A.; DA SILVA, S. C.; MARTIN, R. V.; TAKIISHI, H.; LANDGRAF, F. J. G. Properties of hydrogenation-disproportionation-desorption-recombination NdFeB powders prepared from recycled sintered magnets. Journal of Applied Physics, v. 111, n. 7 APR 1 2012. Web of Science Citations: 25.