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Projects / Programmes source: ARIS

High-coercivity Nd-Fe-B bonded magnets for automotive applications.

Research activity

Code Science Field Subfield
2.04.02  Engineering sciences and technologies  Materials science and technology  Metallic materials 

Code Science Field
P200  Natural sciences and mathematics  Electromagnetism, optics, acoustics 

Code Science Field
2.05  Engineering and Technology  Materials engineering 
Keywords
permanent magnets, high coercivity magnets, intermetallic alloys, rare earths-transition metals, automotive application, bonded magnets
Evaluation (rules)
source: COBISS
Researchers (4)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  21023  Peter Kernel  Materials science and technology  Researcher  2011 - 2014 
2.  04355  PhD Spomenka Kobe  Materials science and technology  Head  2011 - 2014  767 
3.  26027  PhD Andraž Kocjan  Materials science and technology  Researcher  2011 - 2014  74 
4.  18594  PhD Paul John Mc Guiness  Materials science and technology  Researcher  2011 - 2014  338 
Organisations (2)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  91,921 
2.  1682  KOLEKTOR MOBILITY Upravljanje naložb d.o.o. (Slovene)  Idrija  5034558  251 
Abstract
The move toward all-electric drive trains in the automotive industry means that permanent magnets with better properties are required. In this project we will employ a wide variety of novel techniques and processes to develop high-coercivity Nd-Fe-B magnets through improved microstructural control. The goal of the project will be in processing of ultra-fine microstructures combined with localised Dy, which will pre-start an experimental approach to developing Nd-Fe-B materials using inert-atmosphere melt-spinning. The close-to-nano structures will be quantitatively analysed using scanning and transmission electron microscopy. Detailed analyses of the chemical composition, phase composition, and the grain-boundary observations using high-resolution electron microscopy (HR FEG SEM and HRTEM) equipped with the most advanced analytical techniques, such as EDXS, WDXS, EELS, HAADF-STEM, and FIB, will help to better understand the influence of the microstructure on the final coercivity and enable us to achieve the goal of a high coercivity without compromising the magnetisation. Magnetic measurements will be performed by using vibrating sample magnetometer (VSM), SQUID and PPMS. The second part of the research and development project on Nd-Fe-B bonded magnets will be on the chemical and surface properties of bonded materials, which will enable the highest possible flowabillity of the coated powder in the production tools and the highest amount of active magnetic material in the final product, simultaneously with good mechanical properties. There will be a particular emphasis on anisotropic materials to be used for anisotropic bonded magnets, which will represent a major step forward compared to existing isotropic materials. Within this part of the project, multi-pole magnetisation techniques will be studied. In our research we will look at combining this new type of microstructure with targeted dysprosium at the grain boundaries in an attempt to further boost the localised properties by ensuring the minimum concentration of Dy combined with Fe in the Nd2Fe14B phase to prevent remanence-damaging, anti-ferromagnetic coupling between the 3d and 4f elements. Our innovation is to locate the heavy rare earth only at the grain boundaries, where it can have the greatest benefit to the coercivity, but have the least detrimental effect on the remanence. The second area of the project, to improve the chemical and surface properties of the magnetic material in order to improve the flowability of the coated powder in the production process, leading to better filling and a higher proportion of magnetic material in the finished product, so enhancing the final magnetic properties, will focus on innovative surface additives. Last world reports show extremely bad prognosis about availability of rare earths on the market, but for Slovenia this cannot be a problem for two reasons. Our production in comparison with China is too small to be competitive for them and is no need for embargo. Besides Kolektor is business connected in China and will have undisturbed access to the raw materials in by this a huge advantage on the world market.
Significance for science
Magnetic materials based on intermetallic alloys between rare earth and transition metals, as strongest known permanent magnets up to now, represent a great challenge mainly because their application in hybrid electric vehicles, electric vehicles and wind turbines, which is of vital ecological importance (clean environment, energy saving) The project was focused to exceptional challenges in the field of materials and technologies with the final goal to gain new knowledge for development better sintered and bonded permanent Nd-Fe-B magnets with increased coercivity without losing the magnetization. The final goal of the project was not only to optimize the existing technologies but above all to exceed boundaries of knowledge with the starting-point on existing knowledge in the field of sintered magnets discover new possibilities to achieve topmost properties also in the field of bonded magnets with highly innovative approach. The basis for applied oriented basic research is a combination of nanostructured matrix with directed introduction of heavy rare earth at the grain boundaries and not the grains. Nd-Fe-B permanent magnets play an important role in rapidly-growing renewable energy sector. Unfortunately, their magnetic properties undesirably decrease with increasing operating temperature. To overcome this negative effect heavy-rare-earth elements (HRE), such as dysprosium and terbium, are added in a tetragonal Nd2Fe14B crystal structure. The addition of HRE results in a significant improvement of the coercivity (Hci) due to the increase of the intrinsic resistance to demagnetization. However, due to the extremely high-prices of the HRE elements, scientists were seeking for solutions, which would allow the magnets to maintain their properties at low amounts of HRE. We invented a sophisticated method of microstructure modification by so called grain-boundary diffusion process (GBDP) based on electrophoretic deposition followed by additional thermal treatment. GBDP is based on the diffusion of Dy or Tb along grain-boundaries into the outer parts of Nd2Fe14B grains, thus forming core-shell grains with HRE-rich shell and Nd-Fe-B core. We managed to directly correlate the magnetic properties with the microstructure feature properties, such us grain boundaries, triple pockets and core-shell grains by employing advanced characterization of GBDP magnets with the state of the art electron microscopy techniques. The result of the proposed research enabled us to determine the least possible amount of HRE (Dy/Tb) in the Nd-Fe-B magnets, which still provide excellent magnetic properties at operating temperatures. Part of the project was focused on consolidation of melt-spun ribbons coated by DyF3. We have developed and patented a method for manufacturing fully dense Nd-Fe-B magnets by the wet coating of Nd-Fe-B melt-spun ribbons with DyF3 powder followed by spark plasma sintering and subsequent thermal treatment. The maximum coercivity of 2.5 T, represents a 25% increase over the coercivity of the as-sintered, pure MQU-F sample. By coating of MQU-F powders with REF3 and subsequent heat treatment we managed to increase the coercivity and remanence of powders used for bonded magnets. The results of the project were patented, published in journals with IF higher than average, presented as invited talks at international conferences. Two additional publications were submitted.
Significance for the country
A strong economy is the best promotion for any country, and the technology of sintered and bonded permanent magnets based on rare earth and transition metals will importantly contribute to a better recognition of Slovenian science and its economy. At the same time it will open up new opportunities for Slovenian economic and educational institutes. The indirect impact of the project on society is in energy saving and in a major contribution to improved environmental conditions. Critical future situation in the field of fuel, based on fossil’s stock, is pushing the boundaries in the era of hybrid electric vehicles, electric vehicles. The clean energy demands for the solution such as wind turbines. In all this most important future industry permanent magnets are the vital part and this is why the world’s research is focused on achieving better and stronger magnets. Slovenia with its top research potential in the field and worldwide known industry can became one of the most important European and World players.
Most important scientific results Annual report 2011, 2012, 2013, final report, complete report on dLib.si
Most important socioeconomically and culturally relevant results Annual report 2011, 2012, 2013, final report, complete report on dLib.si
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