In the study, the so-called grain-boundary diffusion process (GBDP) was introduced. This is a post-sintering process, where the diffusion of Dy or Tb along grain-boundaries and into the outer parts of Nd2Fe14B grains occurs and this contributes to a higher local constant of crystalline anisotropy and consequently higher coercivity. The result is a “core-shell” microstructure where the core is represented by the Dy-free Nd2Fe14B phase and the shell is rich on Dy (NdDyFe14B). When rough calculations were made, to figure out how high is the Dy-concentration after GBDP, it was determined that in a whole magnet there is 0,6 wt. % of Dy and magnetic properties are even better or as good as in the case of magnet produced by the conventional powder metallurgy route that contain 6-10 wt. % of Dy. For this reason, GBDP based on EPD is an extremely attractive process, which leads to a large coercivity-improvement (up to 30 %) with a small drop in remanence. The highest coercivities achieved so far were 20 KOe.
COBISS.SI-ID: 25708071
We have successfully implemented the advanced, improved methods of high-resolution scanning electron microscopy (FEGSEM) and energy-dispersive and wavelength-dispersive X-ray spectroscopies (EDS, WDS) for the materials characterization on submicrometer and nanometer-scale and used them in characterization of Tb-doped NdFeB sintered permanent magnets.
COBISS.SI-ID: 25799207
Highly coercive permanent Nd-Fe-B-based magnets were successfully developed from commercially available MQU-F rapidly quenched ribbons with optimized composition by wet coating with DyF3 in isopropanol and subsequent spark plasma sintering and heat-treatment. Highest HCi enhancement was obtained at 2.2 wt.% Dy-fraction, i.e. from 1580 to 2025 kA/m, which is 25 % improvement. When more than 3 wt.% of Dy was added, the coercivity enhancement started to decrease, whereas at 4.8 wt.% the coercivity of as-sintered magnet was lower than it was for non-coated one and it was further decreasing with annealing time.
COBISS.SI-ID: 27437351
As the coordinator of European project ROMEO, I was invited to present the goals of the project and directions in European efforts to round off the Chinese restrictions in rare earth metals. I have also contributed to the roind table discussion on materials used in automotive industry.
COBISS.SI-ID: 26335271
The subject of PhD Thesis was the study of processing parameters to produce Nd-Fe-B magnets with a drastic reduction of heavy rare earth. We successfully prepared the magnets by using electrophoretic deposition followed by sophisticated thermal treatment and achieved the excellent properties with ten times smaller amount of heavy earth added as it is the case in standard metallurgical process. Those magnets can be used at higher temperatures for the application in wind turbines and electric and hybrid vehicles.
COBISS.SI-ID: 268167424