Effect of ball milling and dynamic compaction on magnetic properties of Al2O3/Co(P) composite particles

Abstract

Articles you may be interested inThe evolution of the magnetic properties of composite Al 2 O 3 /Co(P) particles during ball milling and dynamic compaction is investigated. To prepare starting composite particles, the Al 2 O 3 granules were coated with a Co 95 P 5 shell by electroless plating. The magnetic and structural properties of the composite particles are characterized by scanning electron microscopy, X-ray diffraction, and the use of the Physical Property Measurement System. The use of composite core-shell particles as starting powder for mechanoactivation allows to decrease treatment duration to 1 h and to produce a more homogeneous bulk sample than in the case of the mixture of Co and Al 2 O 3 powders. The magnetic properties of the milled composite particles are correlated with changes in the microstructure. Reduction in grain size of Co during milling leads to an increase of the volume fraction of superparamagnetic particles and to a decrease of the saturation magnetization. The local magnetic anisotropy field depends on the amount of hcp-Co phase in sample. The anisotropy field value decreases from 8.4 kOe to 3.8 kOe with an increase in milling duration up to 75 min. The regimes of dynamic compaction were selected so that the magnetic characteristics-saturation magnetization and coercive field-remained unchanged. V C 2014 AIP Publishing LLC.

Structure and magnetism in ball-milled core-shell Al2O3@Co particles

“…The X-ray diffraction patterns of particles both Al 2 O 3 @Co 95 P 5 and Co 95 P 5 were characterized by a set of hcp-Co reflexes supplemented with Al 2 O 3 peaks in the case of composite particles. The peaks of Al 2 O 3 disappeared after 15 minutes of milling [16]. The fact is that a continuous metallic coating of cobalt effectively shields X-ray radiation.…”

“…1 a). Particles of Co 95 P 5 during ball-milling undergo allotropic transformations which results in appearing of fcc-Co(P) phase and subsequent changes in its quantity [10,16]. Similar transformations would occur in the cobalt shell of particles.…”

“…Similar transformations would occur in the cobalt shell of particles. However, the cobalt reflections on the X-ray diffraction pattern are significantly broadened by the milling, making it difficult to reliably estimate the phase composition [16]. Therefore, for phase analysis, we use an indirect method based on measuring the approach to magnetic saturation curves.…”

“…The initial Al 2 O 3 /Co(P) composite particles consist of granular Al 2 O 3 cores (50 mass %), surrounded by a shell of Co 95 P 5 particles. The Co-P particles were deposited on Al 2 O 3 surface by electroless plating [14,15] as described in our previous study [16]. The average size of Al 2 O 3 granules is about 300 nm.…”

Effect of process medium on the synthesis of carbon coated lithium vanadium phosphate composite using rheological phase reaction method

“…the mass of grinding balls, rotation speed and the duration of ball-milling [20e22], while the effects of process medium on ball-milling effectiveness, reaction process and final product are rarely reported. When a solvent is added as the process medium, the obtained rheological phase system becomes much complicated which depends on many interrelated parameters, such as the characteristics of suspension, the nature of interparticle forces, the properties of solvent and the viscosity of rheological phase system [22,23]. Hence, the possible roles of process medium during rheological phase process are multifaceted and much meaningful to be investigated.…”