Rare earth permanent magnets Sm_2(Co, Fe, Cu, Zr)_17 for high temperature applications

Sintered Sm（Coba1FexCu0.1Zr0.03）7.5 （x=0.09-0.21） permanent magnets with higher Fe content were found to have higher remanence Br and maximum energy product （BH）max at room temperature. Br and （BH）max reached maximum of 0.96 T and 176.7 kJ/m^3, respectively at room temperature when the Fe content x reached 0.21. However, the intrinsic coercivity Hci at room temperature increased gradually when the Fe content x increased from 0.09 to 0.15, but when x further increased to 0.21, Hcidecreased. Hci attained its peak value of 2276.6 kA/m with Fe content x=0.15 at room temperature. For magnets with x=0.15, Br, （BH）max and Hc1 reached 0.67 T, 81.2 kJ/m^3 and 509.4 kA/m at 500 ℃, respectively, showing good high temperature stability, which could be used in high temperature applications.

Research and Develop ment of Rare Earth Per manent Magnets in China

The research and development of RE magnets in China were briefly reviewed. The research achievements of RE magnets reach international level. The intermetallic nitrides with ThMn12-type structure of RFe series which possess Chinese proprietary were prepared. The output of RE magnets has ranked second in the world. The production of RE magnets will be steadily expanding with the expiration of NdFeB patent in 2003. Some related data were also presented.

Study on Laser Drilling in Rare Earth Magnets

A Nd/YAG pulse laser is used to drill Sm Co and Nd Fe B permanent magnetic rotor The experimental studies and analysis on the morphology and the phase composition of the drilled rotor are described In the centre of the drilled rotor, there is a hole whose diameter is roughly equal to the girdle size of the Gauss laser beam The hole wall is composed of rapidly fused amorphous matter, whose morphology and composition are obviously different from that before hole drilling The grain in heat affected zone has been fined, but the composition has not changed The experimental results show that the reasonable selection of laser parameters according to physical properties of the materials is necessary in order to improve product quality and production efficiency They also show that the lower laser power, the narrower pulse and the mulitiple drilling are advantageous to the processing for hard brittle materials like rare earth magnets

Development of Strip Casting Technology in Rare Earth Permanent Magnet Alloys and Hydrogen Storage Alloys in China

The SC technique is now being applied widely in material preparation, especially in rare earth functional materials in virtue of its advanced process and high performance product. The applications of SC technique in rare earth permanent magnet alloys and hydrogen storage alloys were analyzed integrative, on the basis of summary of SC technique development in this paper. The paper mainly includes development history of SC technology, effect of SC technology on alloy microstructure, application of SC technology in RE storage hydrogen alloy and sintered Nd-Fe-B alloy, development of SC equipment and SC product industry. At the same time, the paper points out the existing problem of SC products.

An Empirical Study of CAPM’s Applicability to Rare Earth Permanent Magnet Material Stocks

China has the world’s largest reserves of rare earth elements.Rare earth permanent magnet material has always been one of the popular industries in the investment market.CAPM is the basic asset-pricing model in financial economics.There are a number of studies conducted to examine the applicability of CAPM to stock markets in different industries and to investigate the modification method to improve the model’s prediction accuracy.In this study,seven leading enterprises in China’s rare earth permanent magnet material industry listed on the A-share market were selected as the research subjects.Based on CAPM,regression analysis was conducted on the monthly data from March 2016 to February 2022.The results demonstrated that using the β coefficient to explain the risk of China’s rare earth permanent magnet industry is ineffective.The ultimate benefit was less affected by market indexes but mainly by non-systematic risks.CAPM has low applicability to China’s rare earth permanent magnet material industry and requires further improvement.Nevertheless,CAPM still has some guiding significance in making enterprise comparisons and investment decisions.

Effect of Fe Substitution on Magnetic Properties and Radar Wave Absorption of the Y_(2)Co_(17) Rare Earth Soft Magnetic Alloy

The rapid development of information technology leads a demand for high frequency soft magnetic materials with ex-ceptional radar wave absorption properties.A new magnetic material with superior radar wave absorption is explored in this paper.we explored the preparation of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)alloy powders using yttrium oxide as a raw material by a low-cost and short preparation cycle reduction-diffusion process.The crystal structure,intrinsic magnetic properties,high frequency magnetism and radar wave absorption of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)were investigated.These compounds have a perfect magnetic repair of Y_(2)Co_(17) and enable the improvement of the overall magnetic properties of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)compounds.The Y_(2)Co_(17)-xFex/Polyurethane(PU)(x=0.0,1.0,2.0,3.0)absorbers were divided in detail using the zero-reflection mechanism.The results show that all Y_(2)Co_(17)-xFex/PU(x=0.0,1.0,2.0,3.0)absorbers have excellent absorption performance(reflection loss RL is less than-85 dB);in addition,Y_(2)Co_(15)Fe_(2)/PU absorbers and Y_(2)Co_(14)Fe_(3)/PU absorbers are superior candidates for S-band materials.In particular,the perfectly matched frequency fp of the modulated Y_(2)Co_(14)Fe_(3)/PU absorber is shifted to the L-band(1–2 GHz)where early warning radars are located.The Y_(2)Co_(14)Fe_(3)/PU absorber has an effective absorption bandwidth of 300 MHz(1.5–1.8 GHz)at a thickness of 5.230 mm.It can also absorb the full L-band at-4 dB,which has rarely been reported.

Influence of the substitution of Sm, Gd, and Dy for La in La_(0.7)Sr_(0.3)MnO_3 on its magnetic and electric properties and strengthening effect on room-temperature CMR

A series of La0.7-xSmxSr0.3MnO3, La0.7-xGdxSr0.3MnO3, and La0.7-xDyxSr0.3MnO3 （x=0.00, 0.10, 0.20, 0.30） samples were prepared by the solid-state reaction method. The influence of the substitution of Sm, Gd, and Dy for La on the magnetic and electric properties and on the magnetoresistance （MR） was studied through measurements of M-T curves and p-T curves. The results showed that： lattice distortion induced by substitution of Sm, Gd, and Dy for La and extra magnetism of substitution had great influence on the magnetic and electric properties of pcrovskite manganites; substitution of magnetic rare earth element for La was an effective way to change Curie temperature and to strengthen MR in perovskite manganites; and appropriate substitution proportion would generate large MR near room temperature.

Microstructure and magnetic properties of Fe-Co-Nd-Y-B alloys obtained by suction casting method

The phase composition, magnetic properties i.e. coercivity and the magnetic polarization at room temperature for the bulk Fe67Co5Nd3Y6B19 and Fe64Co5Nd6Y6B19 alloys were studied. The bulk amorphous Fe67CosNd3Y6B19 alloy, inhomogeneous in the as-quenched state, crystallized after annealing at 948 K for 0.5 h and consisted of Nd2Fe14B-type, Fe2B and paramagnetic phases. The rapidly solidified Fe64Co5Nd6Y6B19 alloy contained the Nd2Fel4B-type and paramagnetic phases. The annealing of the bulk Fe67CosNd3Y6B19 alloy at 948 K for 0.5 h led to hard magnetic properties. However, the bulk Fe64Co5Nd6Y6B19 alloy exhibited good hard magnetic properties directly after preparation.

Effect of annealing process on magnetic properties of Sm(Co_(0.6)Fe_(0.27)Cu_(0.1)Zr_(0.03))_(7.5) ribbons

Sm（Co0.6Fe0.27Cu0.1Zr0.03）7.5 ribbons were prepared by melt-spun method.The results showed that the remnant magnetization Mr and intrinsic coercivity Hci had a rapid increase when the heating rate increased from 5 to 10 °C/min.But the increase of Mr and Hci were observed to be very little when the heating rate was further increased to 20 °C/min.10 °C/min was the critical heating rate for obtaining high magnetic properties.The maximum values of Mr and Hci reached 0.70 T and 780.1 kA/m when the annealing temperature and annealing time were optimized to be 800 °C and 1 h, respectively.Proper second-step heat treatment could suppress the decrease of Hci when the cooling rate increased from 0.7 to 5 °C/min, which could reduce the cooling time effectively.

Iron recovery and rare earths enrichment from Bayan Obo tailings using Coal-Ca(OH)2-NaOH roasting followed by magnetic separation

The recovery of iron and enrichment of rare earths from Bayan Obo railings were investigated using Coal Ca（OH） 2 NaOH roasting followed by magnetic separation. The influences of roasting temperature, roasting time, coal content, milling time, Ca（OH）2 dosage and NaOH dosage on the iron and rare earths recovery were explored. The results showed that the magnetic concentrate containing 70.01 wt. % Fe with the iron recovery of 94.34G and the tailings of magnetic separation containing 11.46 wt. % rare earth oxides （REO） with the REO recovery of 98. 19% were obtained under the optimum conditions （i. e. , roasting temperature of 650℃, roasting time of 60 min, coal content of 2.0%, milling time of 5 min, and NaOH dosage of 2.0%）. The Ca（OH）2 dosage had no effect on the separation of iron and rare earths. According to the mineralogical and morphologic analysis, the iron and rare earths of Bayan Obo tailings could be utilized in subsequent ironmaking process and hydrometallurgy process.

Microstructure and Magnetic Property Variation with Addition of Rare Earth Element Dy in Co-Ni-Al Ferromagnetic Shape Memory Alloy

The influence of rare earth element Dy on martensitic transformation and magnetic properties of Co-Ni-Al alloy was studied.The results showed that the microstructure of the sample has a dual-phase structure（γ-phase and martensite）.The rare earth element Dy was segregated in Co-richγ-phase and took the place of Co after its addition into the Co-Ni-Al alloy.As Dy content increased to over 0.5at.%,the grain was refined and the rare earth intermetallic compounds Co5 Dy were precipitated inγ-phase.Meanwhile,one-step thermo-elastic martensitic transformation occurred in the sample,wherein the phase transformation temperature significantly increased with rising Dy content.The martensite had a tetragonal L10 structure with a（111）twinning plane.Furthermore,the sample exhibited obvious hysteresis behaviors in the magnetic hysteresis loops.In addition,the saturation magnetization,coercivity,retentivity and magnetocrystalline anisotropy were significantly enhanced owing to the bigger radius of Dy which took the place of Co in the alloy.

Application of high-temperature permanent magnets Sm(Co, Fe, Cu, Zr)_Z in PPM focusing system

Rare earth permanent magnets Sm（Co, Fe, Cu, Zr）z with outstanding performance and high-temperature thermal stability were fabricated. Optimized by Fe content and process, Sm（Co0.72Fe0.15Cu0.1Zr0.03）7.5 magnet with B1〉0.75 T and Hci〉1300 kA/m at 300 ℃ can be obtained. According to the performance data of Sm（Co0.72Fe0.15Cu0.1Zr0.03）7.5, the magnetic field along central axis Bz in periodic permanent magnet （PPM） focusing system was simulated using electromagnetic field analysis software Maxwell 2D/3D. The Bz exhibited typical cosine curve along central axis, and the peak value of Bz was high enough to meet the demand of PPM focusing system at room temperature even at 200±20 ℃. Additionally, a kind of simple cooling structure for PPM focusing system was designed by setting cooling pipe between polepieces. Simulated results showed that smooth cosine curve of Bz was successfully achieved with good control of the thickness of cooling pipe.

Preparation of Sm_2Fe_(17)Alloys in Ca-Sm_2O_3-Fe System

Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion （R-D） method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate of R-D and the amount of Sm in the Sm2Fe17 alloy increase, and the increased amount at lower temperature is higher than that at higher temperature. Moreover, results from contracting core modal show that the peritectic reaction between Sm and Fe is a ratedetermined step in the whole R-D process. The apparent activation energy and the pre-exponential factor for this reaction are 73.74 kJ· mol^ -1 and 7.79 × 10^- 3 respectively.

EFFECT OF Nb ADDITION ON MICROSTRUCTURE OF(Nd,Dy)-(Fe,Co)-B MAGNETS

An addition of Nb up to 2 at.-% into(Nd,Dy)-(Fe,Co)-B alloy causes the formation of dendrite Fe_2Nb and the precipitates in hard magnetic grains.Both increases with increasing Nb content.During sintering,part of Fe_2Nb dissolves within the 2:14:1 grains, and the Fe_2Nb along grain boundaries hinders the growth of 2:14:1 grains.During an- nealing,the dissolved Nb in(?)-phase precipitates out,and this nearby the grain boundary diffuses into Nd-rich phase to form new granular Fe_2Nb and to increase the Nb content in Nd-rich phase,this results in a precipitate-free zone in the(?)-grain near Nd-rich phase.

Recovery of Cassiterite and Topaz Minerals from an Old Metallurgical Dump, Eastern Desert of Egypt

Huge amounts of tailing dumps as a result of mines’ blasting operations were impacting economic and environmental problems. Evaluation of one of these tailing dumps of the Eastern Desert of Egypt showed the presence of reasonable amount of cassiterite mineral reaching 0.199% SnO2. The mineral cassiterite was found as finely disseminated particulates, reached to 5 microns, within varieties of quartz-feldspar-hornblende-biotite granitic formations. In the present study, the processing regime considered from the beginning the alignment between reaching cassiterite mineral liberation size, and its extreme brittleness character. Stirring ball milling technique was applied to produce −0.51 mm product with minimum fines as possible, which was left aside for a separate study. The ground product −0.51 + 0.074 mm was subjected to joint shaking table/dry high intensity magnetic separation techniques after splitting it into two fractions, −0.51 + 0.21 mm and −0.21 + 0.074 mm. Each fraction was separately subjected to “Wilfley” shaking table. At optimum conditions, a shaking table concentrate was obtained with 0.29% SnO2 and an operational recovery reached 96.94% from a feeding contained 0.19% SnO2. The heavies and the two middling products after shaking table were directed separately after dryness to dry high intensity magnetic separation using “Eriez” rare earth roll separator, meanwhile the light fractions were rejected. Mathematically designed experiments were applied to optimize the separation process. At optimum conditions, a final cassiterite concentrate was obtained with 11.25% SnO2, and an operational recovery 94.08%. In addition, a topaz mineral concentrate was separated at splitter angle 65˚.

Physico-chemical properties of 3-methoxy-2-nitrobenzoates of some rare earth elements(Ⅲ)

The complexes of 3-methoxy-2-nitrobenzoates of Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, Gd（Ⅲ）, Tb（Ⅲ）, Er（Ⅲ） and Tm（Ⅲ） with the formula： Ln（C8H6NO5）3·2H2O, where Ln=lanthanides（Ⅲ）, were synthesized and characterized by elemental analysis, Forier transform irtrared （FTIR） spectroscopy, magnetic and thermogravimetric studies and also by X-ray diffraction （XRD） measurements. The complexes had col- ours typical for Ln（Ⅲ） ions. The carboxylate groups bound as bidentate chelating. On heating to 1173 K in air they decomposed in the same way, at first, dehydrated in one step to anhydrous salts, and then decomposed to the oxides of respective metals with intermediate formation of the oxycarbonates. The enthalpy values of the dehydration process changed from 133.72 to 44.50 kJ/mol. Their solubility in water at 293 K was of the order of 10-4 mol/dm3. The magnetic moments of analysed complexes were determined by Gouy＇s method in the range of 76-303 K.

Particle size dependent sinterability and magnetic properties of recycled HDDR Nd-Fe-B powders consolidated with spark plasma sintering

The dependence of the magnetic properties on the particle size of recycled HDDR Nd-Fe-B powders was investigated,with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sintering(SPS).The as received recycled HDDR powder has coercivity(Hci)=830 kA/m and particles in the range from 30 to 700 μm(average 220 μm).After burr milling,the average particle size is reduced to 120 μm and subsequently the Hci of fine(milled) powder was 595 kA/m.Spark plasma sintering was exploited to consolidate the nanograined HDDR powders and limit the abnormal grain coarsening.The optimal SPS-ing of coarse HDDR powder at 750℃for 1 min produces fully dense magnets with Hci=950±100 kA/m which further increases to 1200 kA/m via thermal treatment at 750℃for 15 min.The burr milled fine HDDR powder under similar SPS conditions and after thermal treatment results in Hci=940 kA/m.The fine powder is further sieved down from 630 to less than 50 μm mesh size,to evaluate the possible reduction in Hci in relation to the particle size.The gain in oxygen content doubles for <50 μm sized particles as compared with coarser fractions(>200 μm).The XRD analysis for fractionated powder indicates an increase in Nd2O3 phase peaks in the finer(<100 μm)fractions.Similarly,the Hci reduces from 820 kA/m in the coarse particles(>200 μm) to 460 kA/m in the fine sized particles(<100μm).SPS was done on each HDDR powder fraction under the optimal conditions to measure the variation in Hci and density.The Hci of SPS-ed coarse fraction(>200 μm) is higher than 930 kA/m and it falls abruptly to just 70 kA/m for the fine sized particles(<100 μm).The thermal treatment further improves the Hci to>1000 kA/m only up to 100 μm sized fractions with>90% sintered density.The full densification(>99%) is observed only in the coarse fractions.The loss of coercivity and lack of sinterability in the fine sized particles(<100 μm) are attributed to a very high oxygen content.This implies that during recycling,if good magnetic properties are to be maintained or even increase the HDDR powder particles can be sized down only up to≥100 μm.

Magnetic properties of SmCo-based permanent magnetic films during 25 to 300 ℃

Magnetic properties of the SmCo-based permanent magnetic films prepared on hot substrate with Mo and Cr underlayer without subsequent annealing process were investigated by vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, and en- ergy dispersive X-ray spectroscopy （EDS）. The results showed that the film thickness of the SmCo-based films presented complex effect on the intrinsic coercivity Hci. Optimal Hc~ for the films with Mo underlayer, Cr underlayer, and without underlayer was ob- served with different film thicknesses. Furthermore, the monotonous temperature dependence of Hci was found to be strongly corre- lated with the magnetic parameters for the 3.0 μm thick SmCo7 films with Mo underlayer. From 25 to 300 ℃, the Hci decreased from 281.6 to 211.2 kA/m with a temperature coefficient of-0.091%/℃, exhibiting good temperature stability.

Tremendous enhancement of magnetic performance for Sm(CoFeCuZr)z magnet based on multiscale copper redistribution

Microstructure and magnetic properties were studied for the commercial Sm(Co FeCuZr)_(z) magnets before and after post annealing treatment.The results show that the phases composition and orientation of the magnet do not change after post annealing treatment,but the substantial redistribution of Cu element within multiscale(the microscale crystal grain and the nanoscale cellular structure) is observed simultaneously.In detail,along with the Cu redistribution,the thickness of the Cu-rich Sm(Co,Cu)_(5) cell boundary becomes thinner,and the Cu concentration in the boundary increases sharply.The pinning field of domain walls and corresponding coercivity increase remarkably with slight remanence and maximum energy product loss,and the overall magnetic performance of(BH)_(max)(MGOe)+H_(Cj)(kOe)increases by 54.3% as a result.Moreover,the thermal stability of the magnet improves as well.On the other hand,Cu-lean phenomenon was observed along the grain boundary region,triggering to magnetic domain reversal process and slightly undermining the squareness of the demagnetization curve of the magnet.