Investigation of nanocomposite materials with ultrasoft and high performance hard magnetic properties (original) (raw)
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Advances in Natural Sciences: Nanoscience and Nanotechnology, 2011
In this paper, we present the results of an investigation of the influence of fabrication conditions on the structure and magnetic properties of Nd 10.5−x Fe 83.5−y Co x Nb y B 6 (x = 0-6; y = 1.5-3) nanocomposites prepared by melt-spinning combined with annealing. By changing the quenching rate (by varying the tangential velocity of the copper wheel from 10 m s −1 to 40 m s −1 ), one can select a suitable velocity to obtain an alloy that has good, hard magnetic behavior without annealing. However, the hard magnetic behavior of the alloy is better and more stable when the alloy is quenched at a high rate to create an amorphous state and subsequently annealed in the range of 650-800 • C for 10 min. The results also show that the Co concentration has an important effect on the structure and magnetic properties of the alloys.
Journal of Magnetism and Magnetic Materials, 2006
Amorphous ribbons Fe 73.5Àx Mn x Si 13.5 Nb 3 Cu 1 (x ¼ 1, 3, 5) were prepared by rapid quenching on a single rotated copper wheel. The X-ray patterns show that the as-cast samples are amorphous. The measurements of thermomagnetic curves indicated that the Curie temperature of the amorphous phase of the samples decreased with increasing Mn content. The optimal heat treatment was performed at T a ¼ 535 1C for 1 h and showed that the ultrasoft magnetic properties of nanocomposite materials were obtained. The frequency dependence of magnetoimpedance was measured in the frequency range of 1-10 MHz and at a fixed current of 10 mA. The correlation between the MI effect and the soft magnetic properties is discussed.
Journal of Applied Physics, 2003
The effect of Co replacement for Fe on the microstructure and soft magnetic properties of Fe 78.8Ϫx Co x Nb 2.6 Si 9 B 9 Cu 0.6 (xϭ5 -60) nanocrystalline alloys has been studied for improving the soft magnetic properties of Fe-Si-B-Nb-Cu type alloys at a high frequency range. The magnetic anisotropy constant increases with x, but the coercivity increases when x exceeds 20, indicating that magnetic softness is degraded by replacing Fe with Co. Three-dimensional atom-probe observations have revealed that the number density of Cu-enriched clusters decreases with x, thereby decreasing the number density of the heterogeneous nucleation sites for bcc-Fe primary crystals. In addition, differential scanning calorimetry measurements show that the Cu clustering temperature shifts to a higher temperature with increasing x, suggesting that the kinetics for the Cu clustering decreases as Co content. These experimental results are discussed from the thermodynamical point of view, and the optimized Cu composition to achieve a low coercivity with 40 at % Co has been found.
Journal of the Korean Physical Society, 2008
The crystallization evolution and the soft magnetic properties of a a Finemet-like nanocomposite ribbon, Fe73:5Si17:5B5Nb3Cu1, have been investigated by using dierential scanning calorimetry (DSC) and thermomagnetic measurements. The results show that DSC curve exhibits two clearly exothermal peaks, one at 535 C and the other at 670 C, which are related to crystallization of the -Fe(Si) and the boride phases, respectively. The crystallization activation energy is evaluated by using two models, the Kissinger model and the Johnson-Mehl-Avrami (JMA) model, which are consistent with each other. Ultrasoft magnetic properties are obtained after proper annealing due to the formation of an appropriate volume fraction of nanostructured -Fe(Si) embedded in a residual amorphous matrix to compensate the total magnetostriction. The inuence of the annealing process on the soft magnetic properties of the studied sample was investigated and is discussed.
Preparation and characterization of Fe–Nb–Cu–Si–B-based nanocrystalline soft magnetic materials
Applied Surface Science, 2001
The nanocrystalline state of Fe 73.5 Nb 3 Cu 1 Si 13.5 B 9 ribbons exhibit superior soft magnetic properties with low coercivity, high permeability and moderate saturation induction value. However, due to the metastable nature of the materials, their properties depend very much on the preparation condition and heat treatment schedule. In the present work, the properties of the as-cast ribbons prepared at different nozzle diameter and separation between the quenching wheel and the nozzle were evaluated. The optimum conditions for getting continuous long ribbon from 150 g of ingot were established. The in¯uence of heat treatment to get nanostructure and superior soft magnetic properties for selected ribbons were also studied. The ribbon surface quality was improved by reducing air pockets at the ribbon surface which was in contact with the quenching wheel. #
Journal of Alloys and Compounds, 2014
The effects of relaxation and nanocrystallization on magnetic properties of (Fe 0.5 Co 0.5) 73.5 Si 13.5 B 9 Nb 3 Cu 1 ribbons have been investigated. Ribbons were melt-spun at wheel speed of 38 m/s and then annealed at different temperatures. The results indicated that the relaxation processes shift the Curie temperature of amorphous phase to the higher temperatures. It was also found that through crystallization phenomena the saturation magnetization increases due to the super-exchange between Fe and Co atoms in the crystalline phase. A slight variation in magnetization was observed at 700°C during heating due to the ordering transition in FeCo system. At early stage of crystalline phase nucleation, coercivity increased due to the rearrangement of the amorphous phase in both structure and chemical composition.
Journal of Magnetism and Magnetic Materials, 1999
Fe-rich R (Fe,Co,Nb) B (R"Nd, Pr) alloys consisting of a mixture of exchange-coupled magnetically hard 2 : 14 : 1 and soft Fe(Co) phases have been studied for the development of more economical and medium strength permanent magnets. The nanocomposite structure with a grain size around 15}30 nm is obtained by crystallizing the as-made amorphous melt-spun ribbons. The coercivity is found to depend mainly on the grain size of the soft phase which is very sensitive to the sample composition. The average grain size is about 30 nm in R Fe B , but the microstructure is not homogeneous and there are several large-Fe grains with size up to 50}100 nm. The coercivities are 3.3 kOe in Nd Fe B and 4.9 kOe in Pr Fe B samples. Nb substitution signi"cantly reduces the grain size of-Fe and increases the coercivity. The highest coercivities obtained are 5.5 kOe in Nd (Fe Nb) B and 9.3 kOe in Pr (Fe Nb) B samples. Co substitution for Fe increases the grain size of both the 2 : 14 : 1 phase and-Fe and dramatically decreases the coercivity. Increasing the B content in Co substituted samples leads to the formation of a more homogeneous and "ner microstructure and thus to a partial recovery of the coercivity from 2.3 kOe in Nd ((Fe Co) Nb) B to 4.3 kOe in Nd ((Fe Co) Nb) B and from 2.1 kOe in Pr ((Fe Co) Nb) B to 6.5 kOe in Pr ((Fe Co) Nb) B. It is further found that Co substitution signi"cantly increases the Curie temperature of the 2 : 14 : 1 phase and improves the temperature dependence of the saturation magnetization.
The existence of giant magnetocaloric effect and laminar structure in Fe73.5−xCrxSi13.5B9Nb3Cu1
Journal of Magnetism and Magnetic Materials, 2006
Amorphous soft magnetic ribbons Fe 73.5Àx Cr x Si 13.5 B 9 Nb 3 Cu 1 (x ¼ 1-5) have been fabricated by rapid quenching on a single copper wheel. The differential scanning calorimetry (DSC) patterns showed that the crystallization temperature of a-Fe(Si) phase is ranging from 542 to 569 1C, a little higher than that of pure Finemet (x ¼ 0). With the same annealing regime, the crystallization volume fraction as well as the particle size of a-Fe(Si) crystallites decreased with increasing Cr amount substituted for Fe in studied samples. Especially, the interesting fact is that the laminar structure of heat-treated ribbons on the surface contacted to copper wheel in the fabricating process has been firstly discovered and explained to be related to the existence of Cr in studied samples. The hysteresis loop measurement indicated that there is the pinning of displacement of domain walls. The giant magnetocaloric effect (GMCE) has been found in amorphous state of the samples. After annealing, the soft magnetic properties of investigated nanocomposite materials are desirably improved. r