Ultrafast Particle Size Reduction of Fe_73.9Si_15.5Cu₁Nb₃B_6.6 by High-Energy Milling: Nb₂O₅ as a Marker of Permeability Enhancement and Magnetic Hardening

Abstract

This work is conceived to provide a reproducible and fast method to obtain optimal particle sizes for competitive ultrasoft magnetic applications based on Fe73.9Si15.5Cu1Nb3B6.6 nanostructured particles. In this scenario, partial nanocrystallization of the α-Fe3Si compound is promoted by annealing and subsequent high-energy ball milling processes. The milling is performed in this material, for the first time, by a combination of mixer, vibratory, and planetary ball milling motions. Under these conditions, structural and magnetic properties are tuned as a function of milling time with reduced particle size distributions and maintaining the ultrasoft magnetic character. In addition, drastic electronic and structural changes are observed after a few minutes of milling where the saturation magnetization and initial permeability are strongly influenced by the percentage of the α-Fe3Si nanocrystallites formed. Above 30 minutes of ball milling time, the formation of a low concentration of Nb2O5 clusters is detected by confocal Raman microscopy. This identification is essential since the rejection of the Nb from the amorphous matrix rich in Fe-Nb-B atoms acts as a marker of the seed mechanism that causes the deterioration of the softness character of these nanostructures. Therefore, on the one hand, this work introduces a successful procedure by combined milling processes to optimize the saturation magnetization and permeability with sub-micron particle sizes and, on the other hand, the detection of Nb2O5 clusters is implemented as an influential marker on the magnetic properties of these soft nanostructured particles.

A feasible pathway to stabilize monoclinic and tetragonal phase coexistence in barium titanate-based ceramics

“…Instead, the tetragonal simulation converges well for x = 0.000 and x = 0.075, obtaining χ 2 values of 1.69 and 2.30, respectively, being reliable for a good fit. 35,53 In addition to the BaTiO 3 -based compounds, residual contributions of Ba 2 TiO 4 at 1000 °C were noted with percentages of 1.8(7)%, 0.9(3)%, and 2.1(9)% for x = 0.000, 0.050, and 0.075, respectively. These compounds are considered transient as they tend to vanish with the densification temperature.…”

“…35,52 To corroborate our hypothesis, the morphology and number of contributions of other plane families such as (101)/( 110) and ( 111) are examined, comparing with the (002)/( 200) reflections treated at 1000 ºC for the three compositions taking as reference the P4mm space group 37 (Figures 3b-d values for a good fit. 35,53 In addition to the BaTiO 3 -based compounds, residual contributions of Ba 2 TiO 4 at 1000 °C are noted with percentages of 1.8(7)%, 0.9(3)%, and 2.1(9)% for x = 0.000, 0.050, and 0.075, respectively. These compounds are considered transient as they tend to vanish with the densification temperature.…”

Generation of Defective Few-Layered Graphene Mesostructures by High-Energy Ball Milling and Their Combination with FeSiCuNbB Microwires for Reinforcing Microwave Absorbing Properties

“…High-energy oscillatory milling is a technique that provides particle size control but, at the same time, it is a very aggressive method and causes a large number of structural defects. , These structural defects can also influence the interfacial polarization and multiple scattering processes in EM absorbing materials, as studied in interesting studies. ,, One of the techniques capable of revealing the nature of structural defects in carbon-based compounds is the confocal Raman microscopy. − However, care should be taken because it is a local technique, and extensive mappings are required to obtain meaningful information. , …”

“…This container is sealed, and an oscillation frequency of 25 Hz (1500 rpm) is set. During milling, interruptions are scheduled every 20 min to control and maintain the temperature of the container close to room temperature avoiding overheating effects . Then, graphite flakes are subjected to different milling times between 20 and 300 min, where DFLGM samples are favored with different nature of structural defects gradually produced.…”

“…14,26,35,71 Figure 9a shows a typical X-ray diffractogram of such MWs with relatively broad reflections, mainly due to their low-crystal coherence. 26,28 Morphology and size are studied by SEM where the metallic core and Pyrex coating of two MWs can be observed (Figure 9b). To determine the impact on microwave absorption properties and frequency tunability that may result from the addition of DFLGMs in combination with MWs, small amounts of the latter are used below the percolation limit p c .…”