| Partner: F.J. Pedrosa |
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Ostatnie publikacje
| 1. | Guzik M.N.♦, Golasiński K.M.♦, Pedrosa F.J.♦, Jenuš P.♦, Bollero A.♦, Hauback B.C.♦, Deledda S.♦, Influence of ultra-short cryomilling on the microstructural andmagnetic properties of cobalt ferrite, JOURNAL OF ALLOYS AND COMPOUNDS, ISSN: 0925-8388, DOI: 10.1016/j.jallcom.2017.05.290, Vol.721, pp.440-448, 2017 Streszczenie: The impact of ultra-short milling at liquid nitrogen temperatures on structural and magnetic properties of cobalt ferrite (CoFe2O4) powders has been explored for the first time. Cryomilling for only up to 9 min increases the coercivity of the isotropic powder from 139 to 306 kA/m (1.74–3.85 kOe) and results in its modifications comparable with milling for hours at room temperature. A thermal treatment of processed CoFe2O4 enables further optimization of powder magnetic properties and leads to a high value of energy product (13.5 kJ/m3) for the sample treated at 600 °C. Systematic studies, comprising analysis of structural and microstructural properties, based on synchrotron powder X-ray diffraction, scanning and transmission electron microscopy demonstrate the high efficiency of cryomilling in reduction of crystallite sizes and formation of lattice strain in the processed cobalt ferrite samples. Słowa kluczowe: Cryomilling, Cobalt ferrite, Magnetic properties Afiliacje autorów:
|  | 35p. | |||||||||||||||||||||||||||
| 2. | Pedrosa F.J.♦, Rial J.♦, Golasiński K.M.♦, Guzik M.N.♦, Quesada A.♦, Fernández J.F.♦, Deledda S.♦, Camarero J.♦, Bollero A.♦, Towards high performance CoFe2O4 isotropic nanocrystalline powder for permanent magnet applications, APPLIED PHYSICS LETTERS, ISSN: 0003-6951, DOI: 10.1063/1.4969064, Vol.109, No.22, pp.223105-1-4, 2016 Streszczenie: We report on a comparative study of high performance isotropic cobalt ferrite (CoFe2O4) powder processed by dry and surfactant assisted (wet) ball milling. Milling times as short as 1.5 min (dry) and 6 min (wet) have resulted in a 4-fold increase in coercivity, with a maximum achieved value above 318 kA/m (4 kOe). The use of surfactant is shown to be advantageous in the formation of a more homogeneous structure constituted by non-agglomerated and strained nanoparticles. A record (BH) max value of 18.6 kJ m −3 (2.34 MGOe) has been obtained for isotropic powder after post-processing annealing. This magnetic performance combined with the required short processing times and the unnecessary requirement of oxygen avoidance in the milling process, makes this CoFe2O4 powder a good candidate for permanent magnet applications. Słowa kluczowe: Milling, Nanopowders, Powders, Coercive force, Surfactants Afiliacje autorów:
| | 35p. | |||||||||||||||||||||||||||
| 3. | Pedrosa F.J.♦, Rial J.♦, Golasiński K.M.♦, Rodriguez Osorio M.♦, Salas G.♦, Granados D.♦, Camarero J.♦, Bollero A.♦, Tunable nanocrystalline CoFe2O4 isotropic powders obtained by co-precipitation and ultrafast ball milling for permanent magnet applications, RSC Advances, ISSN: 2046-2069, Vol.6, pp.87282-87287, 2016 Streszczenie: Synthesis of nanocrystalline Co-ferrite powders with tunable magnetic properties is demonstrated by using co-precipitation and a novel ultrafast milling route. Milling times as short as a few minutes are re- ported for the first time to be sufficient to refine microstructure and to induce microstrain, and act efficiently, providing a 5-fold increase in coercivity. This is achieved with no compositional change during processing, but exclusively through microstructural modification. The efficiency of this process and its feasible scalability pave the way for development of Co-ferrite powders for permanent magnet applications. Afiliacje autorów:
| | 30p. |