FeCo Nanowire-Strontium Ferrite Powder Composites for Permanent Magnets with High-Energy Products

Due to the issues associated with rare-earth elements, there arises a strong need for magnets with properties between those of ferrites and rare-earth magnets that could substitute the latter in selected applications. Here, we produce a high remanent magnetization composite bonded magnet by mixing FeCo nanowire powders with hexaferrite particles. In the first step, metallic nanowires with diameters between 30 and 100 nm and length of at least 2 {\mu}m are fabricated by electrodeposition. The oriented as-synthesized nanowires show remanence ratios above 0.76 and coercivities above 199 kA/m and resist core oxidation up to 300 {\deg}C due to the existence of a > 8 nm thin oxide passivating shell. In the second step, a composite powder is fabricated by mixing the nanowires with hexaferrite particles. After the optimal nanowire diameter and composite composition are selected, a bonded magnet is produced. The resulting magnet presents a 20% increase in remanence and an enhancement of the energy product of 48% with respect to a pure hexaferrite (strontium ferrite) magnet. These results put nanowire-ferrite composites at the forefront as candidate materials for alternative magnets for substitution of rare earths in applications that operate with moderate magnet performance

Imán permanente, procedimiento de obtención y usos

Imán permanente, procedimiento de obtención y usos. La presente invención se refiere a un imán permanente que comprende partículas magnéticas duras y una estructura magnética blanda con relación de aspecto mayor o igual a 3 y con estructura magnética de monodominio. Además, la presente invención se refiere al procedimiento de obtención de dicho imán y al uso de dicho imán como parte de un generador o un vehículo automóvil. La presente invención se encuadra en el sector de los materiales magnéticos y sus aplicaciones industriales.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad Complutense de Madrid, General Numerics Research Lab E.VA1 Solicitud de patente con informe sobre el estado de la técnic

FeCo nanowire−strontium ferrite powder composites for permanent magnets with high-energy products

Due to the issues associated with rare-earth elements, there arises a strong need for magnets with properties between those of ferrites and rare-earth magnets that could substitute the latter in selected applications. Here, we produce a high remanent magnetization composite bonded magnet by mixing FeCo nanowire powders with hexaferrite particles. In the first step, metallic nanowires with diameters between 30 and 100 nm and length of at least 2 μm are fabricated by electrodeposition. The oriented as-synthesized nanowires show remanence ratios above 0.76 and coercivities above 199 kA/m and resist core oxidation up to 300 °C due to the existence of a >8 nm thin oxide passivating shell. In the second step, a composite powder is fabricated by mixing the nanowires with hexaferrite particles. After the optimal nanowire diameter and composite composition are selected, a bonded magnet is produced. The resulting magnet presents a 20% increase in remanence and an enhancement of the energy product of 48% with respect to a pure hexaferrite (strontium ferrite) magnet. These results put nanowire−ferrite composites at the forefront as candidate materials for alternative magnets for substitution of rare earths in applications that operate with moderate magnet performance.We would like to thank Dr. Vić tor Fuertes for his advice on the processing of the bonded magnets. This work is supported by the Spanish Ministerio de Economía y Competitividad y Ministerio de Ciencia e Innovación (Project Nos. MAT2017- 86450-C4-1-R, MAT2015-64110-C2-1-P, MAT2015-64110- C2-2-P, MAT2017-87072-C4-2-P, RTI2018-095303-A-C52, and FIS2017-82415-R) and by the European Commission through Project H2020 (No. 720853; AMPHIBIAN). C.G.-M. acknowledges financial support from MICINN through the “Juan de la Cierva” Program (FJC2018-035532-I). A.Q. acknowledges financial support from MICINN through the “Ramón y Cajal” Program (RYC-2017-23320). The work also is funded by the Regional Government of Madrid (Project S2018/ NMT-4321; NANOMAGCOST)