Influence of Co＋Nb on the Nd8Fe82Co3Nb1B6 nanocomposite magnets was investigated by adding Co element combined with Nb element. Results show that the high temperature stability of two phases is increased. Adding Co＋...Influence of Co＋Nb on the Nd8Fe82Co3Nb1B6 nanocomposite magnets was investigated by adding Co element combined with Nb element. Results show that the high temperature stability of two phases is increased. Adding Co＋Nb could improve the glass forming ability of the alloy, reduce the size of grains, increase the exchange coupling ability of two phases, and obviously increase the magnetic properties of the alloy. The optimal magnetic properties are Br=1.14 T, Hcj=320 kA/m, （BH）max=109.3 kJ/m^3展开更多
Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy p...Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.展开更多
Multiscale simulation is a key research tool in the quest for new permanent magnets.Starting with first principles methods,a sequence of simulation methods can be applied to calculate the maximum possible coercive fie...Multiscale simulation is a key research tool in the quest for new permanent magnets.Starting with first principles methods,a sequence of simulation methods can be applied to calculate the maximum possible coercive field and expected energy density product of a magnet made from a novel magnetic material composition.Iron(Fe)-rich magnetic phases suitable for permanent magnets can be found by means of adaptive genetic algorithms.The intrinsic properties computed by ab initio simulations are used as input for micromagnetic simulations of the hysteresis properties of permanent magnets with a realistic structure.Using machine learning techniques,the magnet’s structure can be optimized so that the upper limits for coercivity and energy density product for a given phase can be estimated.Structure property relations of synthetic permanent magnets were computed for several candidate hard magnetic phases.The following pairs(coercive field(T),energy density product(kJ·m^-3))were obtained for iron-tin-antimony(Fe3Sn0.75Sb0.25):(0.49,290),L10-ordered iron-nickel(L10 FeNi):(1,400),cobalt-iron-tantalum(CoFe6Ta):(0.87,425),and manganese-aluminum(MnAl):(0.53,80).展开更多
The 2D transient FEM was used to analyze the starting process of the three phase rare-earth LS-PMSM.By verifying the simulation result with the experiment one, we get the conclusion that it is consistent with the expe...The 2D transient FEM was used to analyze the starting process of the three phase rare-earth LS-PMSM.By verifying the simulation result with the experiment one, we get the conclusion that it is consistent with the experiment result very well.At the same time, by analyzing the situation of the magnetic bridge, we also get the result that the amplitude of EMF waves are changing with the situation of the magnetic poles and we can optimize the motor's structure at the same time.展开更多
The RE-Fe-B permanent magnets have a complex microstructure and they are susceptible to corrosion process. In this paper, the commercial nickel coatings adhesion was investigated. The microstructure of the RE-Fe-B wit...The RE-Fe-B permanent magnets have a complex microstructure and they are susceptible to corrosion process. In this paper, the commercial nickel coatings adhesion was investigated. The microstructure of the RE-Fe-B without coating was analyzed by scanning electronic microscopy and electrochemical techniques. The interface magnet/coating was studied by scanning electron microscopy and the nickel-plated Nd-Fe-B commercial magnets were tested in a salt spray chamber. The ferromagnetic and RE-rich phases were observed. After the anodic polarization curve, a strong intergranular corrosion was observed and the RE-rich phase was preferentially attacked. The interface magnet/Ni coating presented inter-granular corrosion that can affect the nickel coating adherence. This attack had probably occurred during the electrodeposition process. Not all the samples suffered localized corrosion during the salt spray tests and the Ni triple-layer coating presented a few corrosion points. RE-Fe-B alloy magnets need to be protected with appropriate coatings to each environment to which they will be exposed and the protective coating must not be damaged.展开更多
Dynamic crystallization was introduced to improve the magnetic properties of NdFeB nanocrystalline permanent magnets by optimizing microstructure.The microstructure was studied by X-ray diffraction(XRD)and transmissio...Dynamic crystallization was introduced to improve the magnetic properties of NdFeB nanocrystalline permanent magnets by optimizing microstructure.The microstructure was studied by X-ray diffraction(XRD)and transmission electron microscopy(TEM).It has been determined that,compared with the conventional heat treatment,dynamic crystallization can shorten the crystallization time.Moreover,dynamic crystallization can refine grains,enhance the exchange-coupled interaction among grains,and promote the magnetic properties.As a result,the optimal magnetic properties of Nd_(10.5)(FeCoZr)_(83.4)B_(6.1)(B_(r)=0.685 T,H_(ci)=732 kA·m^(-1),H_(cb)=429 kA·m^(-1),(BH)_(m)=75 kJ·m^(-3))are obtained after dynamic crystallization heat treatment at 700℃for 10 min.展开更多
Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets.Firstly,rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precu...Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets.Firstly,rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precursors using the hot-pressing process.The prepared isotropic precursors are then hot-deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets and a highly textured structure is produced via this process.The resulting magnets possess many advantages such as near-net-shape,outstanding corrosion resistance,and ultrafine-grain structure.The influence of the preparation parameters utilized in the hot-pressing and deformation processes on the magnetic properties and microstructure of the permanent magnets are systemically summarized in this report.As a near-net-shape technique,the hot deformation process has notable advantages with regard to the production of irregular shapes,especially for radially oriented ringshaped magnets with high length-diameter ratios or thin walls.The difficulties associated with the fabrication of crack-free,homogeneous,and non-decentered ring-shaped magnets are substantially resolved through an emphasis on mold design,adjustment of deformation parameters,and application of theoretical simulation.Considering the characteristics of hotdeformed magnets which include grain shape and size,anisotropic distribution of intergranular phases,etc.,investigation and improvement of the mechanical and electric properties,in addition to thermal stability,with the objective of improving the application of hot-deformed magnets or ring-shaped magnets,is of practical significance.展开更多
The present study reported the influence of heavy rare-earth elements(Gd and/or Dy)on Sm-Co-based melt-spun ribbons.Microstructure and magnetic properties of Sm-Co-based(Sm_(1-x)RE_(x)Co_(5))ternary and quaternary sys...The present study reported the influence of heavy rare-earth elements(Gd and/or Dy)on Sm-Co-based melt-spun ribbons.Microstructure and magnetic properties of Sm-Co-based(Sm_(1-x)RE_(x)Co_(5))ternary and quaternary systems were investigated.The X-ray diffraction,Auger spectroscopy,scanning electron microscopy(SEM)and transmission electron microscopy(TEM)analyses reveal the presence of the 1:5H and 2:17R phases in the as-spun ribbons.A high-temperature magnetic measurement reports a Curie temperature(Tc)at~825 and~869 K in Sm0.6Gd0.4Co5(ribbon A)and Sm_(0.6)Gd_(0.3)Dy_(0.1)Co_(5)(ribbon B),respectively.A low-temperature magnetic measurement on Sm0.6Gd0.3Dy0.1Co5 ribbons exhibits a type-2 SR(spin reorientation)behaviour at~72 K,which arises due to the presence of the DyCo5 phase.Room temperature magnetic measurements reveal that overall magnetic measurement(OMP)is about 24 and 29.9 for ribbons A and B,respectively.Consequently,the comparative investigations profess that ribbon B shows better magnetic performance due to Dy addition with reduced grain size.This observation indicates that the Gd and Dy substituted Sm-Co magnet can be a potential magnet for high-temperature applications.展开更多
LaCo_(13) has the highest 3d metal content ,of any known rare-earth intermetallic compounds,a1. 03MA/m saturation magnetization at room temperature and a high T_c (1318K). Unfortunately ,it is cubic ,lacking of the ne...LaCo_(13) has the highest 3d metal content ,of any known rare-earth intermetallic compounds,a1. 03MA/m saturation magnetization at room temperature and a high T_c (1318K). Unfortunately ,it is cubic ,lacking of the necessary anisotropy,thus diminishing the chance that it will be used as a permanent rnagneticmaterial. In this paper ,the structure and magnetic properties of LaCo_(13) Six (x=2 , 4 )and LaCo_(13) Ge_X(x=2,2. 5 ,3 ,4)intermetallic compounds have been studied. The crystal structure was found to be tetragonal whenx=4 for LaCo_(13-X) Six and x=3 , 4 for LaCo_(13-X) Gex ,but the difference between the lattice parameters a and c isvery small. In order to gain the tetragonal structure ,the annealing temperature of LaCo_(13-X) Ge_X must be con-trolled strictly. The magnetic rneasurement results show that the Curie temperatures of all these compoundsare high ,but the saturation magnetization at room-temperature decreases greatly with x increasing.展开更多
It is well known that the permanent magnet materials are widely used in industry, medical treatment and daily life. Since the discovery of Sm-Co rare-earth transition-metal magnets, the researchers on magnetic materia...It is well known that the permanent magnet materials are widely used in industry, medical treatment and daily life. Since the discovery of Sm-Co rare-earth transition-metal magnets, the researchers on magnetic materials have made great efforts trying to substitute Co by Fe so as to obtain Fe-based rare-earth permanent magnet materials with low cost. The success in producing Nd<sub>2</sub>Fe<sub>14</sub>B permanent magnet has given a new impetus to the study on ironrich rare-earth alloys.展开更多
Samarium–cobalt rare-earth（Sm–Co-RE） permanent magnetic materials with large magnetic energy product, high coercive force, high Curie temperature, good thermal stability, and corrosion resistance, have wide potent...Samarium–cobalt rare-earth（Sm–Co-RE） permanent magnetic materials with large magnetic energy product, high coercive force, high Curie temperature, good thermal stability, and corrosion resistance, have wide potential applications in aerospace, microwave communications, instrumentation, electrical engineering, magnetic machinery, etc. In this paper, the development of Sm–CoRE permanent magnetic materials in the following aspects in recent years was summarized： Sm–Co-RE permanent magnets with high application temperatures, positive temperature coefficients of coercive force, zero temperature coefficients of residual magnetization, high resistance rate,high mechanical property, and nanocrystallization.展开更多
The influence of hard magnetic phase on the crystallization kinetics and magnetization behavior in nanocomposite RE3.5Fe66.5Co10B20（RE = Pr, Nd） ribbons prepared by melt-spinning was studied. Differential scanning c...The influence of hard magnetic phase on the crystallization kinetics and magnetization behavior in nanocomposite RE3.5Fe66.5Co10B20（RE = Pr, Nd） ribbons prepared by melt-spinning was studied. Differential scanning calorimeter（DSC） measurement of the as-cast meltspun amorphous ribbons during the crystallization process shows that precipitation energy of Pr2Fe14 B phase is higher than that for Nd2Fe14 B phase, confirmed by X-ray diffraction（XRD） patterns. It can be explained by the different radii of Pr and Nd atoms. Scanning electron microscopy（SEM）images indicate that the average grain size in Pr3.5Fe66.5Co10B20 ribbon is smaller than that in Nd3.5Fe66.5Co10B20,resulting in an enhancement of exchange coupling between hard and soft phases. It is responsible for the better hard magnetic properties in Pr3.5Fe66.5Co10B20. In addition, the process of magnetization reversal of nanocomposite RE3.5Fe66.5Co10B20（RE = Pr, Nd） ribbons was discussed in detail by the recoil loops.展开更多
Since the discovery of R<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> by Coey and Sun Hong, the intrinsic and extrinsic magnetic properties of these nitrides have been extensively invest...Since the discovery of R<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> by Coey and Sun Hong, the intrinsic and extrinsic magnetic properties of these nitrides have been extensively investigated. Having very good intrinsic magnetic properties with Curie temperature of 749 K and room temperature anisotropy field of 14 T superior to Nd<sub>2</sub>Fe<sub>14</sub>B, and room temperature saturation magnetization of 1.5 T, the Sm<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> nitride is expected to become new permanent magnet for application. The Sm<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> nitride with intrinsic coercivity of 3T has been obtained by mechanical alloying. The Sm<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub>, magnets bonded by metal zinc have intrinsic coercivity μ<sub>0i</sub>H<sub>c</sub> over 0.5 T and magnetic product （BH）<sub>max</sub>about 80 kJ·m<sup>-3</sup>展开更多
Magnetic nanocomposite material has been widely focused for the potential to become the next generation of magnetic material.In this paper,two kinds of chemical coating methods were used to prepare SmCo_(5)/Co nanocom...Magnetic nanocomposite material has been widely focused for the potential to become the next generation of magnetic material.In this paper,two kinds of chemical coating methods were used to prepare SmCo_(5)/Co nanocomposite particles which were further characterized and compared.The two methods were carried out by using different materials and at different temperatures.In Method I,oleylamine(OAm),oleic acid and Ca(acac)2 were used and the reaction was carried out at the temperature of 300℃.In MethodⅡ,anhydrous isopropanol,polyvinylpyrrolidone(PVP),N_(2)H_(4)·H_(2)O and CoCl_(2)·6 H_(2)O were used and the reaction temperature was~55℃.It was found that by using the two methods,the growth and the crystal structure of the Co nanoparticles(NPs)are different.In Method I,epitaxial growth on the surface of SmCo_(5) NPs was observed and the Co NPs were in a facecentered close packing crystal structure.While in Method II,the coated Co NPs were self-nucleated with a crystal structure of hexagonal close packing.Using MethodⅡwith the addition of surfactant,anisotropic nanocomposite particles were achieved with an enhanced saturated magnetization of 84.2 A·m^(2)·kg^(-1).And the coercivity change of the NPs illustrates that a nonmagnetic interlayer between the hard and soft magnetic phase is beneficial to maintain the coercivity.展开更多
基金Funded by the IAR Foundation of Guiyang (No. 2008-I-24-9)
文摘Influence of Co＋Nb on the Nd8Fe82Co3Nb1B6 nanocomposite magnets was investigated by adding Co element combined with Nb element. Results show that the high temperature stability of two phases is increased. Adding Co＋Nb could improve the glass forming ability of the alloy, reduce the size of grains, increase the exchange coupling ability of two phases, and obviously increase the magnetic properties of the alloy. The optimal magnetic properties are Br=1.14 T, Hcj=320 kA/m, （BH）max=109.3 kJ/m^3
基金supported by the National Basic Research Program of China(No.2010CB934601)the National Natural Science Foundation of China(NSFC)(Nos.51125001,51172005,and 90922033)+1 种基金the Doctoral Program(No.20120001110078)the Natural Science Foundation of Beijing(No.2122022)
文摘Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.
基金This work was supported by the EU H2020 project NOVAMAG(686056)and the Austrian Science Fund FWF(I3288-N36).Sergiu Arapan and Pablo Nieves acknowledge the European Regional Development Fund in the IT4Innovations National Supercomputing Center—path to exascale project(CZ 02.1.01/0.0/0.0/16-013/0001791)within the Operational Programme Research,Development and Education,and IT4Innovations computational resources allocated within projects OPEN-11-33,OPEN-14-23,and OPEN-17-14.
文摘Multiscale simulation is a key research tool in the quest for new permanent magnets.Starting with first principles methods,a sequence of simulation methods can be applied to calculate the maximum possible coercive field and expected energy density product of a magnet made from a novel magnetic material composition.Iron(Fe)-rich magnetic phases suitable for permanent magnets can be found by means of adaptive genetic algorithms.The intrinsic properties computed by ab initio simulations are used as input for micromagnetic simulations of the hysteresis properties of permanent magnets with a realistic structure.Using machine learning techniques,the magnet’s structure can be optimized so that the upper limits for coercivity and energy density product for a given phase can be estimated.Structure property relations of synthetic permanent magnets were computed for several candidate hard magnetic phases.The following pairs(coercive field(T),energy density product(kJ·m^-3))were obtained for iron-tin-antimony(Fe3Sn0.75Sb0.25):(0.49,290),L10-ordered iron-nickel(L10 FeNi):(1,400),cobalt-iron-tantalum(CoFe6Ta):(0.87,425),and manganese-aluminum(MnAl):(0.53,80).
文摘The 2D transient FEM was used to analyze the starting process of the three phase rare-earth LS-PMSM.By verifying the simulation result with the experiment one, we get the conclusion that it is consistent with the experiment result very well.At the same time, by analyzing the situation of the magnetic bridge, we also get the result that the amplitude of EMF waves are changing with the situation of the magnetic poles and we can optimize the motor's structure at the same time.
文摘The RE-Fe-B permanent magnets have a complex microstructure and they are susceptible to corrosion process. In this paper, the commercial nickel coatings adhesion was investigated. The microstructure of the RE-Fe-B without coating was analyzed by scanning electronic microscopy and electrochemical techniques. The interface magnet/coating was studied by scanning electron microscopy and the nickel-plated Nd-Fe-B commercial magnets were tested in a salt spray chamber. The ferromagnetic and RE-rich phases were observed. After the anodic polarization curve, a strong intergranular corrosion was observed and the RE-rich phase was preferentially attacked. The interface magnet/Ni coating presented inter-granular corrosion that can affect the nickel coating adherence. This attack had probably occurred during the electrodeposition process. Not all the samples suffered localized corrosion during the salt spray tests and the Ni triple-layer coating presented a few corrosion points. RE-Fe-B alloy magnets need to be protected with appropriate coatings to each environment to which they will be exposed and the protective coating must not be damaged.
基金This work was financially supported by New Century Excellent Person Support Program of China(No.NCET-04-0873)Science Found for Distinguished Young Scholars of Sichuan Province(No.03ZQ026-006)Major Science Plan of Sichuan Province(No.03GG009-006).
文摘Dynamic crystallization was introduced to improve the magnetic properties of NdFeB nanocrystalline permanent magnets by optimizing microstructure.The microstructure was studied by X-ray diffraction(XRD)and transmission electron microscopy(TEM).It has been determined that,compared with the conventional heat treatment,dynamic crystallization can shorten the crystallization time.Moreover,dynamic crystallization can refine grains,enhance the exchange-coupled interaction among grains,and promote the magnetic properties.As a result,the optimal magnetic properties of Nd_(10.5)(FeCoZr)_(83.4)B_(6.1)(B_(r)=0.685 T,H_(ci)=732 kA·m^(-1),H_(cb)=429 kA·m^(-1),(BH)_(m)=75 kJ·m^(-3))are obtained after dynamic crystallization heat treatment at 700℃for 10 min.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0700902)the National Natural Science Foundation of China(Grant Nos.51671207,51601207,and 51501213)
文摘Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets.Firstly,rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precursors using the hot-pressing process.The prepared isotropic precursors are then hot-deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets and a highly textured structure is produced via this process.The resulting magnets possess many advantages such as near-net-shape,outstanding corrosion resistance,and ultrafine-grain structure.The influence of the preparation parameters utilized in the hot-pressing and deformation processes on the magnetic properties and microstructure of the permanent magnets are systemically summarized in this report.As a near-net-shape technique,the hot deformation process has notable advantages with regard to the production of irregular shapes,especially for radially oriented ringshaped magnets with high length-diameter ratios or thin walls.The difficulties associated with the fabrication of crack-free,homogeneous,and non-decentered ring-shaped magnets are substantially resolved through an emphasis on mold design,adjustment of deformation parameters,and application of theoretical simulation.Considering the characteristics of hotdeformed magnets which include grain shape and size,anisotropic distribution of intergranular phases,etc.,investigation and improvement of the mechanical and electric properties,in addition to thermal stability,with the objective of improving the application of hot-deformed magnets or ring-shaped magnets,is of practical significance.
文摘The present study reported the influence of heavy rare-earth elements(Gd and/or Dy)on Sm-Co-based melt-spun ribbons.Microstructure and magnetic properties of Sm-Co-based(Sm_(1-x)RE_(x)Co_(5))ternary and quaternary systems were investigated.The X-ray diffraction,Auger spectroscopy,scanning electron microscopy(SEM)and transmission electron microscopy(TEM)analyses reveal the presence of the 1:5H and 2:17R phases in the as-spun ribbons.A high-temperature magnetic measurement reports a Curie temperature(Tc)at~825 and~869 K in Sm0.6Gd0.4Co5(ribbon A)and Sm_(0.6)Gd_(0.3)Dy_(0.1)Co_(5)(ribbon B),respectively.A low-temperature magnetic measurement on Sm0.6Gd0.3Dy0.1Co5 ribbons exhibits a type-2 SR(spin reorientation)behaviour at~72 K,which arises due to the presence of the DyCo5 phase.Room temperature magnetic measurements reveal that overall magnetic measurement(OMP)is about 24 and 29.9 for ribbons A and B,respectively.Consequently,the comparative investigations profess that ribbon B shows better magnetic performance due to Dy addition with reduced grain size.This observation indicates that the Gd and Dy substituted Sm-Co magnet can be a potential magnet for high-temperature applications.
文摘LaCo_(13) has the highest 3d metal content ,of any known rare-earth intermetallic compounds,a1. 03MA/m saturation magnetization at room temperature and a high T_c (1318K). Unfortunately ,it is cubic ,lacking of the necessary anisotropy,thus diminishing the chance that it will be used as a permanent rnagneticmaterial. In this paper ,the structure and magnetic properties of LaCo_(13) Six (x=2 , 4 )and LaCo_(13) Ge_X(x=2,2. 5 ,3 ,4)intermetallic compounds have been studied. The crystal structure was found to be tetragonal whenx=4 for LaCo_(13-X) Six and x=3 , 4 for LaCo_(13-X) Gex ,but the difference between the lattice parameters a and c isvery small. In order to gain the tetragonal structure ,the annealing temperature of LaCo_(13-X) Ge_X must be con-trolled strictly. The magnetic rneasurement results show that the Curie temperatures of all these compoundsare high ,but the saturation magnetization at room-temperature decreases greatly with x increasing.
文摘It is well known that the permanent magnet materials are widely used in industry, medical treatment and daily life. Since the discovery of Sm-Co rare-earth transition-metal magnets, the researchers on magnetic materials have made great efforts trying to substitute Co by Fe so as to obtain Fe-based rare-earth permanent magnet materials with low cost. The success in producing Nd<sub>2</sub>Fe<sub>14</sub>B permanent magnet has given a new impetus to the study on ironrich rare-earth alloys.
基金financially supported by the Research Fund for the Doctoral Program of Higher Education of China (No.20100560)the National Natural Science Foundation of China (Nos. 51104188 and 51274107)
文摘Samarium–cobalt rare-earth（Sm–Co-RE） permanent magnetic materials with large magnetic energy product, high coercive force, high Curie temperature, good thermal stability, and corrosion resistance, have wide potential applications in aerospace, microwave communications, instrumentation, electrical engineering, magnetic machinery, etc. In this paper, the development of Sm–CoRE permanent magnetic materials in the following aspects in recent years was summarized： Sm–Co-RE permanent magnets with high application temperatures, positive temperature coefficients of coercive force, zero temperature coefficients of residual magnetization, high resistance rate,high mechanical property, and nanocrystallization.
基金financially supported by the Project of Zhejiang Province Innovative Research Team (No. 2010R50016)the Provincial Natural Science Foundation (No. LQ12E01006)the National natural Science Foundation of China (No. 51301158)
文摘The influence of hard magnetic phase on the crystallization kinetics and magnetization behavior in nanocomposite RE3.5Fe66.5Co10B20（RE = Pr, Nd） ribbons prepared by melt-spinning was studied. Differential scanning calorimeter（DSC） measurement of the as-cast meltspun amorphous ribbons during the crystallization process shows that precipitation energy of Pr2Fe14 B phase is higher than that for Nd2Fe14 B phase, confirmed by X-ray diffraction（XRD） patterns. It can be explained by the different radii of Pr and Nd atoms. Scanning electron microscopy（SEM）images indicate that the average grain size in Pr3.5Fe66.5Co10B20 ribbon is smaller than that in Nd3.5Fe66.5Co10B20,resulting in an enhancement of exchange coupling between hard and soft phases. It is responsible for the better hard magnetic properties in Pr3.5Fe66.5Co10B20. In addition, the process of magnetization reversal of nanocomposite RE3.5Fe66.5Co10B20（RE = Pr, Nd） ribbons was discussed in detail by the recoil loops.
文摘Since the discovery of R<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> by Coey and Sun Hong, the intrinsic and extrinsic magnetic properties of these nitrides have been extensively investigated. Having very good intrinsic magnetic properties with Curie temperature of 749 K and room temperature anisotropy field of 14 T superior to Nd<sub>2</sub>Fe<sub>14</sub>B, and room temperature saturation magnetization of 1.5 T, the Sm<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> nitride is expected to become new permanent magnet for application. The Sm<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub> nitride with intrinsic coercivity of 3T has been obtained by mechanical alloying. The Sm<sub>2</sub>Fe<sub>17</sub>N<sub>y</sub>, magnets bonded by metal zinc have intrinsic coercivity μ<sub>0i</sub>H<sub>c</sub> over 0.5 T and magnetic product （BH）<sub>max</sub>about 80 kJ·m<sup>-3</sup>
基金financially supported by the National Key R&D Program of China(No.2018YFB2003901)National Natural Science Foundations of China(NSFC)(No.51520105002)。
文摘Magnetic nanocomposite material has been widely focused for the potential to become the next generation of magnetic material.In this paper,two kinds of chemical coating methods were used to prepare SmCo_(5)/Co nanocomposite particles which were further characterized and compared.The two methods were carried out by using different materials and at different temperatures.In Method I,oleylamine(OAm),oleic acid and Ca(acac)2 were used and the reaction was carried out at the temperature of 300℃.In MethodⅡ,anhydrous isopropanol,polyvinylpyrrolidone(PVP),N_(2)H_(4)·H_(2)O and CoCl_(2)·6 H_(2)O were used and the reaction temperature was~55℃.It was found that by using the two methods,the growth and the crystal structure of the Co nanoparticles(NPs)are different.In Method I,epitaxial growth on the surface of SmCo_(5) NPs was observed and the Co NPs were in a facecentered close packing crystal structure.While in Method II,the coated Co NPs were self-nucleated with a crystal structure of hexagonal close packing.Using MethodⅡwith the addition of surfactant,anisotropic nanocomposite particles were achieved with an enhanced saturated magnetization of 84.2 A·m^(2)·kg^(-1).And the coercivity change of the NPs illustrates that a nonmagnetic interlayer between the hard and soft magnetic phase is beneficial to maintain the coercivity.
