Improved thermal stability of hard magnetic properties in rapidly solidified RE–TM–B alloys

2008 ◽  
Vol 23 (10) ◽  
pp. 2733-2742 ◽  
Author(s):  
Z.W. Liu ◽  
R.V. Ramanujan ◽  
H.A. Davies
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Magnetic Properties ◽  
Elevated Temperature ◽  
Melt Spinning ◽  
Maximum Energy ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Rapidly Solidified ◽  
Hard Magnetic Properties

Rapidly solidified nanocrystalline RE–TM–B (RE = Nd, Pr, Dy, TM = Fe, Co) alloys with enhanced hard magnetic properties were synthesized by melt spinning. The composition- and microstructure-dependent elevated temperature magnetic properties were investigated. The temperature coefficients of remanence (α) and coercivity (β) were determined. The effects of Pr substituting Nd, Co substituting Fe, Dy substituting RE, and grain size on the Curie temperature and thermal stability were studied. Co or Dy substitutions were found to have a significant beneficial effect on the thermal stability. Reducing grain size could also improve elevated temperature behavior. Maximum energy product (BH)max > 100 kJ/m3 could be obtained in compositionally optimized nanophase alloys at temperature of 473 K. Extremely low coefficients of α and β were realized in exchange coupled nanocomposite alloys. Bonded nanocomposite magnets with α = −0.052%/K and β = −0.0365%/K for 300–400 K were also successfully fabricated.

EM of rapidly solidified permanent magnets

1992 ◽  
Vol 50 (1) ◽  
pp. 198-199
Author(s):  
Raja K. Mishra
Keyword(s):  
Melt Spinning ◽  
Permanent Magnets ◽  
Dark Field Image ◽  
Dark Field ◽  
Maximum Energy ◽  
Quench Rate ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Annular Dark Field ◽  
Rapidly Solidified

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.

Effect of Dysprosium Content on the Magnetic Properties of Nanocrystalline (Pr0.25Nd0.75)10-xDyxFe82Co2B6 Alloys

2014 ◽  
Vol 789 ◽  
pp. 28-31 ◽  
Author(s):  
He Wei Ding ◽  
Chun Xiang Cui ◽  
Ji Bing Sun
Keyword(s):  
Magnetic Properties ◽  
Melt Spinning ◽  
Maximum Energy ◽  
Vibrating Sample Magnetometer ◽  
X Ray ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Intrinsic Coercivity ◽  
Electronic Microscope ◽  
Microstructure And Magnetic Properties

(Pr0.25Nd0.75)10-xDyxFe82Co2B6(x=0~0.3) ribbons were prepared by melt spinning at 25m/s and subsequent annealing. The effect of Dy content on the microstructure and magnetic properties of the ribbons has been investigated by X-ray diffractometer (XRD), scanning electronic microscope (SEM) and vibrating sample magnetometer (VSM). The magnetic properties related to the Dy content were characterized. Intrinsic coercivity of 598kA/m, remanence of 0.58T, and the maximum energy product (BH)max of 43kJ/m3 were achieved in (Pr0.25Nd0.75)9.8Dy0.2Fe82Co2B6 after annealing at 700°C for 10 minutes.

Magnetic Domain Structure of Nanocrystalline Zr18-xHfxCo82 Ribbons: Effect of Hf

2013 ◽  
Vol 1557 ◽  
Author(s):  
Lanping Yue ◽  
I. A. Al-Omari ◽  
Wenyong Zhang ◽  
Ralph Skomski ◽  
D. J. Sellmyer
Keyword(s):  
Magnetic Properties ◽  
Domain Structure ◽  
Structure Refinement ◽  
Magnetic Domain ◽  
Maximum Energy ◽  
Magnetic Domain Structure ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Domain Structures ◽  
Rapidly Solidified

ABSTRACTThe effect of Hf on the permanent magnetism of nanocrystalline Zr18-xHfxCo82 ribbons (x = 0, 2, 4, and 6) was investigated by magnetic properties measurement and magnetic force microscopy (MFM). Emphasis is on the local magnetic domain structures in polycrystalline rapidly solidified Zr18-xHfxCo82 ribbons for four different samples with small fractions of Hf dopants (x ≤ 6). The investigation of the magnetic properties of the Zr18-xHfxCo82 ribbons revealed that all the samples under investigation are ferromagnetic at room temperature, and the corresponding MFM images show bright and dark contrast patterns with up-down magnetic domain structures. It is found that the saturation magnetization and the coercivity depend on Hf doping concentration x in the samples. For a sample with Hf concentration x = 4, the maximum energy product (BH)max value is 3.7 MGOe. The short magnetic correlation length of 131 nm and smallest root-mean-square phase shift value of 0.680 were observed for x = 4, which suggests the refinement of the magnetic domain structure due to weak intergranular exchange coupling in this sample. The above results indicate that suitable Hf addition is helpful for the magnetic domain structure refinement, the coecivity enhancement, and the energy-product improvement of this class of rare-earth-free nanocrystalline permanent-magnet materials.

Influence of Milling Time on Magnetic Properties and Microstructure of Sintered Nd-Fe-B Based Permanent Magnets

2018 ◽  
Vol 930 ◽  
pp. 445-448
Author(s):  
R.G.T. Fim ◽  
M.R.M. Silva ◽  
S.C. Silva ◽  
Julio Cesar Serafim Casini ◽  
P.A.P. Wendhausen ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Permanent Magnets ◽  
Milling Time ◽  
Maximum Energy ◽  
Inhomogeneous Distribution ◽  
Maximum Energy Product ◽  
Grain Sizes ◽  
Energy Product

In this paper, the effect of the grain size on sintered Nd-Fe-B based permanent magnets was investigated. In order, the magnets were produced by different milling times at 200 rpm and then vacuum sintered at 1373 K for 60 minutes followed by cooling outside the furnace. The magnets either produced by lower and higher milling times (30 and 75 minutes) exhibited lower remanence and coercivity, due the inhomogeneous distribution of the grain sizes. The magnet produced by intermediary milling time (45 minutes) exhibited the highest properties among all samples, with remanence of 1.06 T, coercivity of 891.3 KA.m-1, maximum energy product of 211 KJ.m3and a squareness factor equal 0.92.

scholarly journals Fabrication and Magnetic Properties of \(\text{Nd}_2\text{Fe}_{14}\text{B/Fe}_{65}\text{Co}_{35}\) Hard Magnetic Ribbons

2013 ◽  
Vol 23 (2) ◽  
pp. 147
Author(s):  
Nguyen Xuan Truong ◽  
Nguyen Van Khanh
Keyword(s):  
Magnetic Properties ◽  
Free Surface ◽  
Melt Spinning ◽  
Maximum Energy ◽  
Homogeneous Distribution ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Magnetic Remanence ◽  
Intrinsic Coercivity ◽  
Melt Spinning Technique

Nd\(_2\)Fe\(_{14}\)B/Fe\(_{65}\)Co\(_{35}\) hard magnetic ribbons were fabricated by melt-spinning technique using Nd\(_{16}\)Fe\(_{76}\)B\(_{8 }\) and Fe\(_{65}\)Co\(_{35}\) pre-alloys as starting materials. The results showed that the formation of the interactive hard/soft nanocomposite with the homogeneous distribution of the Fe-Co phase throughout the Nd\(_{2}\)Fe\(_{14}\)B matrix provided the Curie temperature (\(T_{c})\) as high as 747 K, the magnetic remanence (B\(_{r}\)) of 8.88 kG and the maximum energy product, (BH)\(_{\max}\), of 16.75 MG.Oe for the fabricated Nd\(_{2}\)Fe\(_{14}\)B/Fe\(_{65}\)Co\(_{35}\) ribbons at the optimal speed of 25 m/s. In addition, the intrinsic coercivity (\(_{i}\)H\(_{c}\)) of 9.27 kOe and remanence coercivity (\(_{b}\)H\(_{c}\)) of 6.94 kOe were found for these ribbons. The roles of the soft Fe\(_{65}\)Co\(_{35}\) phase in the increasing of \(T_{c}\), \(B_{r}\) as well as in the (00l) preferred crystallographic orientation of hard magnetic grains on the free surface side of the fabricated ribbons were also discussed.

Effects of Magnetic Powder Loading on Mechanical Properties and Magnetic Properties of Natural Rubber

2006 ◽  
Vol 45 ◽  
pp. 1423-1428
Author(s):  
Somsak Woramongconchai ◽  
Chatchawan Lohitvisat ◽  
Aree Wichainchai
Keyword(s):  
Mechanical Properties ◽  
Magnetic Properties ◽  
Coercive Force ◽  
Natural Rubber ◽  
Barium Ferrite ◽  
Maximum Energy ◽  
Magnetic Powder ◽  
Elongation At Break ◽  
Maximum Energy Product ◽  
Energy Product

The effect of magnetic powders and powders loading on magnetic properties and mechanical properties of magnetic rubbers were studied. The natural rubber with magnetic powders, Barium ferrite, Neodymium iron boron, were used as starting materials to prepare magnetic rubbers. Barium ferrite (BaO.6F2O3) powders had been sintered at 1285 oC for 30 hours to improve its crystal structure. The physical properties of magnetic rubbers, residual flux density (Br), coercive force (Hc), maximum energy product (BHmax), hardness and density, had a trend to increase as enhancing magnetic powders loading. However, some properties such as, intrinsic coercive force (Hci), tensile strength and elongation at break, had a trend to decrease when the magnetic powder loading was increased. Magnetic properties of the anisotropic type, sintered powders, were higher than isotropic type, non-sintered powders, except the Hci because anisotropic magnetic rubber indicated crystal orientation in the same direction.

Bulk metallic glass formation, composite, and magnetic propertiesof Fe-B-Nd based alloys

2009 ◽  
Vol 24 (2) ◽  
pp. 357-371 ◽  
Author(s):  
J. Zhang ◽  
Y.P. Feng ◽  
Y. Li
Keyword(s):  
Glass Formation ◽  
Magnetic Phase ◽  
Industrial Applications ◽  
Maximum Energy ◽  
Quaternary Alloys ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Hard Magnets ◽  
Hard Magnet ◽  
Hard Magnetic Properties

The glass formation in Fe-rich ternary Fe-B-Nd and quaternary (Fe,B,Nd)96Nb4 alloys has been studied and the best ternary and quaternary glass formers are located at Fe67B23Nd10 and (Fe68B25Nd7)Nb4 with critical diameters of 1 and 4 mm, respectively. For (Fe,B,Nd)96Nb4 alloys, the competing phases with glass were identified by monitoring the microstructure change. Fe14Nd2B was discovered to be one competing phase, which is the principle magnetic phase for Nd-Fe-B hard magnets. Composites with uniformly distributed Fe14Nd2B were formed for quaternary alloys with a diameter of 1.5 to 3 mm. Bulk hard magnets could be obtained by directly annealing the composites in a compositional area. A hard magnet with a coercivity of 1,100 kAm−1 and a maximum energy product, (BH)max, of 33 kJm–3 was obtained at (Fe67B23Nd10)96Nb4 by annealing. The combination of hard magnetic properties and the large critical sample size may make these alloys a commercially viable candidate for industrial applications.

New YDy-Based R2(Fe,Co)14B Melt-Spun Magnets (R=Y+Dy+Nd)

2005 ◽  
Vol 475-479 ◽  
pp. 2155-2160 ◽  
Author(s):  
W. Tang ◽  
K.W. Dennis ◽  
Matthew J. Kramer ◽  
I.E. Anderson ◽  
R.W. McCallum
Keyword(s):  
Magnetic Properties ◽  
High Temperature ◽  
Temperature Coefficient ◽  
Temperature Stability ◽  
Maximum Energy ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Optimal Sample ◽  
Melt Spun ◽  
Nd Substitution

The effects of the ratio of Y to Dy as well as the effect of Nd and Co substitutions on magnetic properties in [Ndx(YDy)0.5(1-x)]2.2Fe14-yCoyB ribbons melt-spun at 22 m/s have been systematically studied. (Y1-zDyz)2.2Fe14B ribbons with a ratio z of 0.25 or 0.5 simultaneously obtains a smaller temperature coefficient of remanence (α ) and coervicity (β ) which are much smaller than those of Nd-based Nd2Fe14B ribbons. In [Ndx(YDy)0.5(1-x)]2.2Fe14-yCoyB ribbons, Nd substitution (x=0 to 0.8) can improve the maximum energy product (BH)max of annealed ribbons but degrades the temperature stability of the magnetic properties. The ribbons with x=0.4 and y=0 yield a (BH)max of 8.7 MGOe. For these ribbons, the α and β are -0.07 and -0.31 %/°C in the temperature range of 27 to 127°C, respectively. Increasing Co (x) from 0 to 3, slightly decreases coercivity Hcj from 21.5 to 16.3 kOe, but keeps the (BH)max in the range of 8.6 to 10.2 MGOe. The optimal sample with x=0.5 and y=1.5 obtains a (BH)max of 10.2 and 5.0 MGOe at 27 and 250°C, respectively. Its α and β are -0.11 and -0.30 %/°C, respectively. These results show that studied ribbons are very promising to develop into high temperature isotropic bonded magnets capable of operating at or above 180°C.

scholarly journals Nanocrystalline Nd-Fe-B Alloys for Polymer-Bonded Magnets Production

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
Aleksandar Grujić ◽  
Vladan Ćosović ◽  
Aleksandar Ćosović ◽  
Jasna Stajić-Trošić
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Magnetic Phase ◽  
Coupling Effect ◽  
Maximum Energy ◽  
Soft Magnetic ◽  
Nanocomposite Structure ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Composite Production

This study presents how different nanostructures of starting Nd-Fe-B particles have influence on magnetic properties of polymer-bonded Nd-Fe-B materials. Two types of nanocrystalline Nd-Fe-B alloys were used for polymer composite production by compression molding technique. The particles with low neodymium content (Nd-low) have nanocomposite structure with small exchange coupling effect between hard and soft magnetic phase. In other hand, practically monophase hard magnetic structure of Nd-Fe-B particles with stoichiometric neodymium content (Nd-stoich) shows improved magnetic properties. With increasing concentration of polymer matrix, the coercivity (Hcb), remanence (Br), and maximum energy product ((BH)max) decrease more prominenty for composites with stoichiometric Nd-Fe-B content.

scholarly journals Development of a High-Performance-Ferrite Magnet Fabrication Process without Sintering Additives

2021 ◽  
Vol 59 (8) ◽  
pp. 551-559
Author(s):  
Pyeong-Yeol Yu ◽  
Min-Ho Kim ◽  
Young-Min Kang
Keyword(s):  
Magnetic Properties ◽  
Saturation Magnetization ◽  
High Performance ◽  
Secondary Phase ◽  
Batch Process ◽  
Maximum Energy ◽  
Magnetic Flux Density ◽  
Sintering Additives ◽  
Energy Product ◽  
Hard Magnetic Properties

Sintered M-type hexaferrites with the chemical formula of Sr0.3Ca0.4La0.3Fe9.8Co0.2-xMnxSi0.135O19-d (x = 0, 0.05, 0.1, 0.2) and Sr0.3Ca0.4La0.3Fe9.8-yCo0.2MnySi0.135O19-d (y = 0.05, 0.1, 0.2) were prepared by conventional solid station reaction routes. A high sintering density of more than 95% of the theoretical density was achieved in all hexaferrite samples when calcination was carried out at 1100 oC for 4 h, followed by sintering at 1230-1250 oC for 2 h without the use of sintering additives. High saturation magnetization and coercivity were achieved simultaneously at the x = 0.05 composition, where Mn replaces part of the Co. The secondary phase Fe2O3 generated by the initial addition of SiO2 was gradually reduced when the Fe contented was decreased in the Sr0.3Ca0.4La0.3Fe9.8-zCo0.15Mn0.05Si0.135O19-d samples, and a single M-type hexaferrite phase was confirmed in the Sr0.3Ca0.4La0.3Fe8.3Co0.15Mn0.05Si0.135O19-d (z = 1.5) sample, which also exhibited optimized hard magnetic properties, with a saturation magnetization of 4581 G and coercivity of 4771 Oe. Anisotropic sintered magnets were fabricated using the optimized composition, and showed excellent hard magnetic properties, with a remanent magnetic flux density of 4400 G and intrinsic coercivity of 4118 Oe, and a maximum energy product of 4.72 M·G·Oe. This result is very promising because high magnet performance can be achieved with a single batch process without the need for sintering additives during the process.

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