Structure and phases of low-neodymium NdFeB permanent magnets

2006 ◽  
Vol 56 (S3) ◽  
pp. E45-E50 ◽  
Author(s):  
T. Žák ◽  
N. Talijan ◽  
V. Čosović ◽  
A. Grujić
Keyword(s):  
Author(s):  
Raja K. Mishra

The discovery of a new class of permanent magnets based on Nd2Fe14B phase in the last decade has led to intense research and development efforts aimed at commercial exploitation of the new alloy. The material can be prepared either by rapid solidification or by powder metallurgy techniques and the resulting microstructures are very different. This paper details the microstructure of Nd-Fe-B magnets produced by melt-spinning.In melt spinning, quench rate can be varied easily by changing the rate of rotation of the quench wheel. There is an optimum quench rate when the material shows maximum magnetic hardening. For faster or slower quench rates, both coercivity and maximum energy product of the material fall off. These results can be directly related to the changes in the microstructure of the melt-spun ribbon as a function of quench rate. Figure 1 shows the microstructure of (a) an overquenched and (b) an optimally quenched ribbon. In Fig. 1(a), the material is nearly amorphous, with small nuclei of Nd2Fe14B grains visible and in Fig. 1(b) the microstructure consists of equiaxed Nd2Fe14B grains surrounded by a thin noncrystalline Nd-rich phase. Fig. 1(c) shows an annular dark field image of the intergranular phase. Nd enrichment in this phase is shown in the EDX spectra in Fig. 2.


Author(s):  
Mahesh Chandramouli

Magnetization reversal in sintered Fe-Nd-B, a complex, multiphase material, occurs by nucleation and growth of reverse domains making the isolation of the ferromagnetic Fe14Nd2B grains by other nonmagnetic phases crucial. The magnets used in this study were slightly rich in Nd (in comparison to Fe14Nd2B) to promote the formation of Nd-oxides at multigrain junctions and incorporated Dy80Al20 as a liquid phase sintering addition. Dy has been shown to increase the domain wall energy thus making nucleation more difficult while Al is thought to improve the wettability of the Nd-oxide phases.Bulk polished samples were examined in a JEOL 35CF scanning electron microscope (SEM) operated at 30keV equipped with a Be window energy dispersive spectrometer (EDS) detector in order to determine the phase distribution.


Author(s):  
W. Coene ◽  
F. Hakkens ◽  
T.H. Jacobs ◽  
K.H.J. Buschow

Intermetallic compounds of the type RE2Fe17Cx (RE= rare earth element) are promising candidates for permanent magnets. In case of Y2Fe17Cx, the Curie temperature increases from 325 K for x =0 to 550 K for x = 1.6 . X ray and electron diffraction reveal a carbon - induced structural transformation in Y2Fe17Cx from the hexagonal Th2Ni17 - type (x < 0.6 ) to the rhombohedral Th2Zn17 - type ( x ≥ 0.6). Planar crystal defects introduce local sheets of different magnetic anisotropy as compared with the ordered structure, and therefore may have an important impact on the coercivivity mechanism .High resolution electron microscopy ( HREM ) on a Philips CM30 / Super Twin has been used to characterize planar crystal defects in rhombohedral Y2Fe17Cx ( x ≥ 0.6 ). The basal plane stacking sequences are imaged in the [100] - orientation, showing an ABC or ACB sequence of Y - atoms and Fe2 - dumbbells, for both coaxial twin variants, respectively . Compounds resulting from a 3 - week annealing treatment at high temperature ( Ta = 1000 - 1100°C ) contain a high density of planar defects.


1977 ◽  
Vol 38 (C1) ◽  
pp. C1-333-C1-336 ◽  
Author(s):  
P. CAVALLOTTI ◽  
R. ROBERTI ◽  
G. CAIRONI ◽  
G. ASTI

1988 ◽  
Vol 49 (C8) ◽  
pp. C8-573-C8-574
Author(s):  
G. F. Zhou ◽  
X. K. Sun ◽  
Y. C. Chuang ◽  
L. Gao ◽  
Z. Yu ◽  
...  

2020 ◽  
Vol 64 (1-4) ◽  
pp. 977-983
Author(s):  
Koichi Oka ◽  
Kentaro Yamamoto ◽  
Akinori Harada

This paper proposes a new type of noncontact magnetic suspension system using two permanent magnets driven by rotary actuators. The paper aims to explain the proposed concept, configuration of the suspension system, and basic analyses for feasibility by FEM analyses. Two bar-shaped permanent magnets are installed as they are driven by rotary actuators independently. Attractive forces of two magnets act on the iron ball which is located under the magnets. Control of the angles of two magnets can suspend the iron ball stably without mechanical contact and changes the position of the ball. FEM analyses have been carried out for the arrangement of two permanent magnets and forces are simulated for noncontact suspension. Hence, successfully the required enough force against the gravity of the iron ball can be generated and controlled. Control of the horizontal force is also confirmed by the rotation of the permanent magnets.


2020 ◽  
Vol 64 (1-4) ◽  
pp. 1381-1389
Author(s):  
Dezhi Chen ◽  
Chengwu Diao ◽  
Zhiyu Feng ◽  
Shichong Zhang ◽  
Wenliang Zhao

In this paper, a novel dual-stator permanent magnet machine (DsPmSynM) with low cost and high torque density is designed. The winding part of the DsPmSynM adopts phase-group concentrated-coil windings, and the permanent magnets are arranged by spoke-type. Firstly, the winding structure reduces the amount of copper at the end of the winding. Secondly, the electromagnetic torque ripple of DsPmSynM is suppressed by reducing the cogging torque. Furthermore, the dynamic performance of DsPmSynM is studied. Finally, the experimental results are compared with the simulation results.


1989 ◽  
Author(s):  
Nicholas J. Grant ◽  
R. C. O'Handley ◽  
N. J. Grant
Keyword(s):  

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