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
Magnetization and demagnetization curves and hysteresis loops applied different magnetizing.fields in sintered Nd-Fe-B and Nd-Dy-Fe-B magnets from thermally demagnetized and dc field-demagnetized states were investiga...Magnetization and demagnetization curves and hysteresis loops applied different magnetizing.fields in sintered Nd-Fe-B and Nd-Dy-Fe-B magnets from thermally demagnetized and dc field-demagnetized states were investigated at temperatures of up to 150℃.The first-quadrant remagnetization curves and the curves of coercive forces _MH_C versus rernagnetizing fietds H_m from dc field-demagnetized state at room temperature show a step around magnetizing field as absolute value of the maximum intrinsic coercivity.The steps of _MH_C-H_m curves shifted to lower remagnetizing fields and the shapes of magnetization curves changed from step type to precipitous type when temperature went up to 100～150℃ or after the specimen was thermally demagnetized at a temperature higher than the Curie temperature.The steep rise of knee coereivity with increasing magnetizing field is behind that of _MH_C.Note that the magnetic hardening in sintered Nd-Fe-B magnets is controlled by pinning of domain walls.展开更多
Effect of thermal annealing on the magnetization reversal behavior of α-Fe/Nd2Fe14B alloys was investigated. A drastic in- crease of the remanence Mr from 0.67 up to 0.87 T and remanence ratio Mr/Ms from 0.66 up to 0...Effect of thermal annealing on the magnetization reversal behavior of α-Fe/Nd2Fe14B alloys was investigated. A drastic in- crease of the remanence Mr from 0.67 up to 0.87 T and remanence ratio Mr/Ms from 0.66 up to 0.76, respectively, was observed in the α-Fe/NdEFel413 alloys annealed at 610 ℃ as compared with the as-quenched sample. Whereas the further annealing at 680 ℃ resulted in a strong increase of the corecivity Hc as high as 491 kA/m but a slight decrease in Mr. The analysis result of the magnetization re- versal behavior showed that the maximum value of the integrated recoil loop area about 1.58 kJ/m3 was obtained in the α-Fe/Nd2Fe14B alloys at the annealing temperature of 610℃, significantly lower than other annealed samples. This indicated a sig- nificant advantage for the application of this material as permanent magnets in electrical machines and generators due to a low energy loss.展开更多
The Fe−Ni−TiO_(2) nanocomposite coatings were electrodeposited by pulse frequency variation.The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at h...The Fe−Ni−TiO_(2) nanocomposite coatings were electrodeposited by pulse frequency variation.The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies.By increasing the pulse frequency from 10 to 500 Hz,the iron and TiO_(2) nanoparticles contents were increased in expense of nickel content.XRD patterns showed that by increasing the frequency to 500 Hz,an enhancement of BCC phase was observed and the grain size of deposits was reduced to 35 nm.The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO_(2) nanoparticles into the Fe−Ni matrix(5.13 wt.%).Moreover,the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased.展开更多
In this study,a magnetic high entropy alloy(HEA)of CoFeMn_(1.2)NiGa_(0.8)was designed and prepared by arc melting in order to investigate its mechanical,corrosion and magnetic behavior.The results show that the alloy ...In this study,a magnetic high entropy alloy(HEA)of CoFeMn_(1.2)NiGa_(0.8)was designed and prepared by arc melting in order to investigate its mechanical,corrosion and magnetic behavior.The results show that the alloy mainly possesses body-centered cubic(BCC)phase and face-centered cubic(FCC)phase.A high compressive strength of 1450 MPa,a strain of 18.5%and a relatively low yield strength of 303MPa in as-cast condition at room temperature can be achieved in the present alloy.In-situ high-energy X-ray diffraction technique was employed to reveal the deformation mechanism of Co Fe Mn_(1.2)Ni Ga_(0.8)under uniaxial compression and the results show that the competition between BCC phase and FCC phase plays a significant role during the compressive process.The corrosion behavior of Co Fe Mn_(1.2)Ni Ga_(0.8)was investigated in 3.5 wt%Na Cl solution and it turned out that the alloy possessed good corrosion resistance.At last,the magnetic behavior of the Co Fe Mn_(1.2)Ni Ga_(0.8)alloy was studied and it can present a high saturation magnetization of 94.5 emu/g and a coercivity of 26.4 Oe at 4 K.This work indicates that the present Co Fe Mn_(1.2)Ni Ga_(0.8)HEA has promising applications as future magnetic functional materials.展开更多
The successful discovery of borophene has opened a new door for the development of 2D materials.Due to its excellent chemical,electronic and thermal properties,borophene has shown considerable potential in supercapaci...The successful discovery of borophene has opened a new door for the development of 2D materials.Due to its excellent chemical,electronic and thermal properties,borophene has shown considerable potential in supercapacitors,hydrogen storage and batteries.In this paper,the thermodynamic characteristics and magnetocaloric effect of borophene are specifically studied using the Monte Carlo method.We find that there is an opposite impact between the spin quantum number and the crystal field on the magnetization,magnetic susceptibility,specific heat and magnetic entropy of the system.Moreover,increasing the spin quantum number or decreasing the absolute value of the crystal field can improve the relative cooling power,the coercivity(h_(c)),and the remanence(M_(R))and the area of the loop.展开更多
Molecules with multifunctional properties are of immense interest in hybrid materials, while challenges still existed because of the limited compatibility of multiple functionalities in a single system. In this work, ...Molecules with multifunctional properties are of immense interest in hybrid materials, while challenges still existed because of the limited compatibility of multiple functionalities in a single system. In this work, a series of metal-organic complexes were synthesized and characterized under the assembly of electron donor phosphonate, electron acceptor polypyridine ligand and spin carrier rare earth ions. All the compounds exhibited remarkable and reversible responses with photochromism and photomodulated fluorescence, originated from photogenerated radicals via electron transfer from phosphonates to polypyridine ligands. For the Dy analog, slow magnetic relaxation was observed at cryogenic temperature, indicating the single-molecule magnetic behavior. Furthermore, photogenerated radicals could enhance the proton conductive behavior, with about 2 times larger in magnitude after light irradiation for Dy and Y compounds. The introduction of photoluminescence, magnetism and proton conduction into metallic phosphonates can provide potential applications for photochromic materials.展开更多
The particle interaction during magnetization reversal process is important for the applications and magnetic properties improvement of Sm2Fe17Nx powders. In this paper, an anisotropic Sm2Fe17Nx powder free of α- Fe ...The particle interaction during magnetization reversal process is important for the applications and magnetic properties improvement of Sm2Fe17Nx powders. In this paper, an anisotropic Sm2Fe17Nx powder free of α- Fe was prepared by ball milling. The magnetically soft Sm2Fe17 powders with different particle sizes were added into the α-Fe-free SmaFe17Nx powder as easy nucleation sites, and the effects of these magnetically soft phases on the magnetization reversal process were investigated quantitatively. It is found that the squareness of Sm2Fe17Nx powder decreases obviously with the increasing number of Sm2Fe17 particle and the demagnetization curves can be divided into two stages. The magnetization reversal process suggests that the addition of magnetically soft powder should only reduce the coercivity of a specific part of Sm2Fe17Nx particles and the reversed domain walls cannot move easily across neighboring Sm2Fe17Nx particles. Based on the observed magnetization reversal process, the mechanical properties of magnetically soft phase should be considered in the preparation of anisotropic Sm2Fe17Nx powders.展开更多
The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz<= f<=25000 Hz and 0.1 T< =Bm <=1.0 T for three main original magnetic states in five sorts of Fe-base...The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz<= f<=25000 Hz and 0.1 T< =Bm <=1.0 T for three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys. The measured and calculated results showed that the total power loss per cycle clearly exhibited a nonlinear behavior in the range below 3 kHz～5 kHz depending on both the magnetic state and the value of Dm, whereas it showed a quasi-linear behavior above this range. The total loss was decomposed into hysteresis loss, classical eddy current loss and excess loss, the obvious nonlinear behavior has been confirmed to be completely determined by the dependence of the excess loss on frequency. It has been indicated that the change rate of the excess loss per cycle with respect to frequency sharp decreases with increasing frequency in the range below about 3 kHz～5 kHz, wherease the rate of change slowly varies above this range, thus leading to the quasilinear behavior of the total loss per cycle. In this paper, some linear expressions of the total loss per cycle has been given in a wider medium-frequency segment, which can be used for roughly estimating the total loss.展开更多
Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice...Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice and the absorptive oxygen bonds at the surface are carefully examined. The absorptive oxygen bond is about 50% of the total oxygen bond by using a semi-quantitative method. The value of actual stoichiometry δ′ is close to 2. The experimental results indicate that the thin films are of a cerium oxide-based solid solution with few oxygen vacancies in the lattice and many absorptive oxygen bonds at the surface. Week ferromagnetic behaviors were evidenced by observed M-H hysteresis loops at room temperature. Furthermore, an evidence of relative ferromagnetic contributions was revealed by the temperature dependence of magnetization. It is believed that the ferromagnetic contributions exhibited in the M-H loops originate from the absorptive oxygen on the surface rather than the oxygen vacancies in the lattice.展开更多
Stress induction plays a special role in performance control for material science.So far,it has remained challenging to systematically investigate magnetoelectric effect under stress-mediated interaction.Here we const...Stress induction plays a special role in performance control for material science.So far,it has remained challenging to systematically investigate magnetoelectric effect under stress-mediated interaction.Here we constructed a magnetoelectric device with piezoelectric stress induction,in which the stress plays a crucial intermediate role during the controllable modification of the magnetic behavior transitions under the magnetic field or current pulse driven process.The compressive stress was found to make the above process easier and reduce energy consumption via changing the magnetic domain energy state.Meanwhile,both the domain distribution and domain-wall driven process are sensitive to stress intensity.Our magnetoelectric device integrated the advantages of voltage-stress and spin-current for the control of magnetic behavior transition with the help of micro-nano processing.For the stress-induced magnetic behavior in magnetic materials was directly imaged and quantificationally investigated,the complex interactions between stress,magnetic domain motion,magnetic field,and spin current have been clarified.展开更多
Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereform...Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereformed, which are properly due to the existing of oxygen in the alloys introduced during the heat treatment process, the magnetic properties of the alloy decrease.展开更多
A novel diamagnetic-metal Cd（Ⅱ） complex with four nitroxide radicals[Cd（IM4Py）4Cl2]（IM4Py=2-（4＇-pyridinyl）-4,4,5,5-tetramethylimidazoline-1-oxyl） was synthesized and characterized by elemental analyses,IR sp...A novel diamagnetic-metal Cd（Ⅱ） complex with four nitroxide radicals[Cd（IM4Py）4Cl2]（IM4Py=2-（4＇-pyridinyl）-4,4,5,5-tetramethylimidazoline-1-oxyl） was synthesized and characterized by elemental analyses,IR spectra,UV-Vis spectra and X-ray single crystal diffraction.The complex crystallized in triclinic space group P1 with a=0.93285（14） nm,b=1.16827（18） nm,c=1.3660（2） nm,α=112.759（2）°,β=104.524（2）°,γ=92.008（3）°,V= 1.3143（3） nm3,Z=1,Dc=1.335 g/cm3,the final R1=0.0423 and wR2=0.1009.In the title complex,each Cd（Ⅱ） ion adopting a distorted octahedral geometry is coordinated by two Cl-anions and four pyridyl-N atoms from four IM4Py ligands.The magnetic measurements show the weak antiferromagnetic interactions between the nitroxide radicals.展开更多
Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/α-Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at gr...Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/α-Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at grain boundaries increases with increasing annealing temperature for the both types of magnets. The increase of this kind of defect can improve the coercivity of the single-phase magnet. Conversely,the increase of vacancy-cluster amount leads to decreasing of the coercivity for the nanocomposite magnet. It implies that the mechanism of dominant magnetic hardening for the two types of magnets is different, and the domain walls pinning mechanism in the single-phase magnet and the reversal magnetization nucleation mechanism in the nanocomposite magnet operate, respectively.展开更多
Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin （2, 5/2） Ising system for the antiferromagnetic/antiferromagnetic （AFM/AFM） interactions...Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin （2, 5/2） Ising system for the antiferromagnetic/antiferromagnetic （AFM/AFM） interactions on the bilayer square lattice under a time varying （sinusoidal） magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic （FM/FM） and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions.展开更多
A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform ele...A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform electric field in a positive column of helium direct current(DC) gas discharge Graphs showing the electron density and energy distributions, and the percentage of electrons that reach the wall and the end of the positive column are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column which are in good agreement with experimental results.展开更多
The nanocrystalline Fe-Ni-Cr coatings were electrodeposited by using the pulse current technique.The SEM results showed that the coatings had a mixed morphology of small nodules and fine cauliflower structures at low ...The nanocrystalline Fe-Ni-Cr coatings were electrodeposited by using the pulse current technique.The SEM results showed that the coatings had a mixed morphology of small nodules and fine cauliflower structures at low current densities.Also,the Cr content was increased at expense of Fe and Ni contents at high current densities.XRD patterns confirmed that the pulse current density had a positive effect on the grain refinement.The results of vibrating sample magnetometer(VSM)measurements demonstrated that by increasing the current density,the saturation magnetization was decreased and the coercivity was increased due to the enhancement of Cr content and the reduction of the grain size.The friction coefficient and wear rate values were decreased by increasing the pulse current density.Also,both the adhesive and abrasive wear mechanisms were observed on the worn surfaces.The abrasive grooves and the amount of wear debris were decreased by increasing the pulse current density.展开更多
A series of novel hexanuclear lanthanide dusters,namely,[Ln_(6)(HL)_(6)(NO_(3))_(6)]·3CH_(3)CN(Ln=Gd(1),Tb(2),Dy(3)and Er(4))was assembled using a multidentate ligand H3L(trolamine).The clusters 1-4 show a wheel-...A series of novel hexanuclear lanthanide dusters,namely,[Ln_(6)(HL)_(6)(NO_(3))_(6)]·3CH_(3)CN(Ln=Gd(1),Tb(2),Dy(3)and Er(4))was assembled using a multidentate ligand H3L(trolamine).The clusters 1-4 show a wheel-shaped Ln_(6)topology with the approximate diameter and thickness of 1.5 and 0.7 nm,respectively.All of them show high thermal stability.In the aspect of the catalytic capacities for the cycloaddition reactions of CO_(2)and epoxide,the reaction conditions,the substrate scope,and possible catalytic mechanism were investigated.The highest yield for clusters 1-4 is up to 99%at 333 K for 12 h.In particular,cluster 1 can be reused at least three times with no obvious loss of catalytic performance and keep the integrity of the crystal structure.Magnetic investigations reveal that cluster 1 exhibits a relatively large magnetocaloric effect with-ΔS_(m)=41.43 J/(kg·K)(T=3.0 K,7.0 T);while cluster 3 displays slow magnetic relaxation behavior under zero dc field with U_(eff)=0.51 K andτ_(0)=2.54×10^(-5)s.展开更多
This paper addresses the manipulation of structural,morphology,optical and magnetic properties of LiCo0.25Zn0.25Fe2 O4 ferrite via incorporation of different proportions of La^3+at the expense of iron ions using a sol...This paper addresses the manipulation of structural,morphology,optical and magnetic properties of LiCo0.25Zn0.25Fe2 O4 ferrite via incorporation of different proportions of La^3+at the expense of iron ions using a sol-gel method.The samples were characterized using the X-ray diffraction technique(XRD),Fourier transform infrared(FT-IR)spectroscopy,the energy dispersive X-ray spectra(EDX),inductively coupled plasma optical emission spectroscopy(ICP-OES),high resolution scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET)surface area analysis,ultraviolet-diffuse reflectance spectroscopy(UV-DRS),and vibrating sample magnetometer(VSM)technique.The Rietveld refinements of the samples indicate that at higher concentrations of La^3+,nanostructures with dual phase,i.e.cubic spinel and orthorhombic LaFeO3 perovskite with space group(Pbnm)appear.Optical studies show that the energy band gap(Eg)of the bare LiCo0.25Zn0.25Fe2 O4 ferrite sample(2.18 eV)reaches up to 2.47 eV at x=0.06 and above this concentration,it drops sharply to 2.00 eV.Although the saturation magnetization and the coercivity of LiCo0.25Zn0.25LaxFe2-xO4 are lower than that of LiCo0.25Zn0.25Fe2 O4 NPs.Overall,the superparamagnetic nature and low values of saturation magnetization and coercivity of LiCo0.25Zn0.25LaxFe2-xO4 NPs are suitable to be applied in transformers core.展开更多
A new type of Ni-P alloy with rod-shape was prepared by electroless deposition method based on the shape of Nocadia, a kind of bacteria. The material was characterized by microbiological method, scanning electron micr...A new type of Ni-P alloy with rod-shape was prepared by electroless deposition method based on the shape of Nocadia, a kind of bacteria. The material was characterized by microbiological method, scanning electron microscope, energy dispersion spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction and vibrant sample magnetometer. It was found that Ni-P alloy deposited on Nocadia surface was amorphous when pH=8.0. The amount of Ni crystalline increased with pH of plating solution. Ni-P nano-particles deposited on active locations on the surface at the initial stage, and then homogeneous Ni-P film formed with time. Nocadia remained their original rod shape after Ni-P nano-particles deposition. The new type metal material formed of Ni-P alloy with nano-particles was prepared. The mag- netization of the material prepared at pH=9.7 is greater than that prepared at pH=8.0. The magnetic loss of the material prepared at pH=9.7 is less than 0.1. The dielectric loss exceeds 0.3 when frequency is higher than 14 GHz, which is 1.5 at 18 GHz. The new type Ni-P metal material with Nocadia shape has dielectric loss property.展开更多
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Magnetization and demagnetization curves and hysteresis loops applied different magnetizing.fields in sintered Nd-Fe-B and Nd-Dy-Fe-B magnets from thermally demagnetized and dc field-demagnetized states were investigated at temperatures of up to 150℃.The first-quadrant remagnetization curves and the curves of coercive forces _MH_C versus rernagnetizing fietds H_m from dc field-demagnetized state at room temperature show a step around magnetizing field as absolute value of the maximum intrinsic coercivity.The steps of _MH_C-H_m curves shifted to lower remagnetizing fields and the shapes of magnetization curves changed from step type to precipitous type when temperature went up to 100～150℃ or after the specimen was thermally demagnetized at a temperature higher than the Curie temperature.The steep rise of knee coereivity with increasing magnetizing field is behind that of _MH_C.Note that the magnetic hardening in sintered Nd-Fe-B magnets is controlled by pinning of domain walls.
基金Foundation item： Project supported by Project of Zhejiang Province Innovative Research Team （2010R50016）, Zhejiang Provincial Natural Science Foundation （Y6100640）, National Natural Science Foundation of China （51001092, 51271172） and National Public Profession Sci- entific Research （201210107）
文摘Effect of thermal annealing on the magnetization reversal behavior of α-Fe/Nd2Fe14B alloys was investigated. A drastic in- crease of the remanence Mr from 0.67 up to 0.87 T and remanence ratio Mr/Ms from 0.66 up to 0.76, respectively, was observed in the α-Fe/NdEFel413 alloys annealed at 610 ℃ as compared with the as-quenched sample. Whereas the further annealing at 680 ℃ resulted in a strong increase of the corecivity Hc as high as 491 kA/m but a slight decrease in Mr. The analysis result of the magnetization re- versal behavior showed that the maximum value of the integrated recoil loop area about 1.58 kJ/m3 was obtained in the α-Fe/Nd2Fe14B alloys at the annealing temperature of 610℃, significantly lower than other annealed samples. This indicated a sig- nificant advantage for the application of this material as permanent magnets in electrical machines and generators due to a low energy loss.
文摘The Fe−Ni−TiO_(2) nanocomposite coatings were electrodeposited by pulse frequency variation.The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies.By increasing the pulse frequency from 10 to 500 Hz,the iron and TiO_(2) nanoparticles contents were increased in expense of nickel content.XRD patterns showed that by increasing the frequency to 500 Hz,an enhancement of BCC phase was observed and the grain size of deposits was reduced to 35 nm.The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO_(2) nanoparticles into the Fe−Ni matrix(5.13 wt.%).Moreover,the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased.
基金support from the National Key Research and Development Program of China(No.2018YFC1902401)National Natural Science Foundation of China(No.51671180)+1 种基金supported by Key Deployment Projects of the Chinese Academy of Sciences(ZDRWCN-2019-01)Projects of the Innovation Academy for Green Manufacture,Chinese Academy of Sciences(IAGM 2020DB04)。
文摘In this study,a magnetic high entropy alloy(HEA)of CoFeMn_(1.2)NiGa_(0.8)was designed and prepared by arc melting in order to investigate its mechanical,corrosion and magnetic behavior.The results show that the alloy mainly possesses body-centered cubic(BCC)phase and face-centered cubic(FCC)phase.A high compressive strength of 1450 MPa,a strain of 18.5%and a relatively low yield strength of 303MPa in as-cast condition at room temperature can be achieved in the present alloy.In-situ high-energy X-ray diffraction technique was employed to reveal the deformation mechanism of Co Fe Mn_(1.2)Ni Ga_(0.8)under uniaxial compression and the results show that the competition between BCC phase and FCC phase plays a significant role during the compressive process.The corrosion behavior of Co Fe Mn_(1.2)Ni Ga_(0.8)was investigated in 3.5 wt%Na Cl solution and it turned out that the alloy possessed good corrosion resistance.At last,the magnetic behavior of the Co Fe Mn_(1.2)Ni Ga_(0.8)alloy was studied and it can present a high saturation magnetization of 94.5 emu/g and a coercivity of 26.4 Oe at 4 K.This work indicates that the present Co Fe Mn_(1.2)Ni Ga_(0.8)HEA has promising applications as future magnetic functional materials.
文摘The successful discovery of borophene has opened a new door for the development of 2D materials.Due to its excellent chemical,electronic and thermal properties,borophene has shown considerable potential in supercapacitors,hydrogen storage and batteries.In this paper,the thermodynamic characteristics and magnetocaloric effect of borophene are specifically studied using the Monte Carlo method.We find that there is an opposite impact between the spin quantum number and the crystal field on the magnetization,magnetic susceptibility,specific heat and magnetic entropy of the system.Moreover,increasing the spin quantum number or decreasing the absolute value of the crystal field can improve the relative cooling power,the coercivity(h_(c)),and the remanence(M_(R))and the area of the loop.
基金supported by the National Natural Science Foundation of China (Nos. 21901133 and 22071126)Key Research and Development Project of Shandong Province (No. 2019GGX102006)the State Key Laboratory of Fine Chemicals (No. KF1905)。
文摘Molecules with multifunctional properties are of immense interest in hybrid materials, while challenges still existed because of the limited compatibility of multiple functionalities in a single system. In this work, a series of metal-organic complexes were synthesized and characterized under the assembly of electron donor phosphonate, electron acceptor polypyridine ligand and spin carrier rare earth ions. All the compounds exhibited remarkable and reversible responses with photochromism and photomodulated fluorescence, originated from photogenerated radicals via electron transfer from phosphonates to polypyridine ligands. For the Dy analog, slow magnetic relaxation was observed at cryogenic temperature, indicating the single-molecule magnetic behavior. Furthermore, photogenerated radicals could enhance the proton conductive behavior, with about 2 times larger in magnitude after light irradiation for Dy and Y compounds. The introduction of photoluminescence, magnetism and proton conduction into metallic phosphonates can provide potential applications for photochromic materials.
基金financially supported by the National Natural Science Foundation of China (No. 51401021)
文摘The particle interaction during magnetization reversal process is important for the applications and magnetic properties improvement of Sm2Fe17Nx powders. In this paper, an anisotropic Sm2Fe17Nx powder free of α- Fe was prepared by ball milling. The magnetically soft Sm2Fe17 powders with different particle sizes were added into the α-Fe-free SmaFe17Nx powder as easy nucleation sites, and the effects of these magnetically soft phases on the magnetization reversal process were investigated quantitatively. It is found that the squareness of Sm2Fe17Nx powder decreases obviously with the increasing number of Sm2Fe17 particle and the demagnetization curves can be divided into two stages. The magnetization reversal process suggests that the addition of magnetically soft powder should only reduce the coercivity of a specific part of Sm2Fe17Nx particles and the reversed domain walls cannot move easily across neighboring Sm2Fe17Nx particles. Based on the observed magnetization reversal process, the mechanical properties of magnetically soft phase should be considered in the preparation of anisotropic Sm2Fe17Nx powders.
文摘The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz<= f<=25000 Hz and 0.1 T< =Bm <=1.0 T for three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys. The measured and calculated results showed that the total power loss per cycle clearly exhibited a nonlinear behavior in the range below 3 kHz～5 kHz depending on both the magnetic state and the value of Dm, whereas it showed a quasi-linear behavior above this range. The total loss was decomposed into hysteresis loss, classical eddy current loss and excess loss, the obvious nonlinear behavior has been confirmed to be completely determined by the dependence of the excess loss on frequency. It has been indicated that the change rate of the excess loss per cycle with respect to frequency sharp decreases with increasing frequency in the range below about 3 kHz～5 kHz, wherease the rate of change slowly varies above this range, thus leading to the quasilinear behavior of the total loss per cycle. In this paper, some linear expressions of the total loss per cycle has been given in a wider medium-frequency segment, which can be used for roughly estimating the total loss.
基金supported by the Natural Science Foundation of Zhejiang Province,China(Grant No.LY12A01002)the National Natural Science Foundation of China(Grant Nos.11204058 and 21073162)the Hangzhou Dianzi University,China(Grant No.KYF09150603)
文摘Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice and the absorptive oxygen bonds at the surface are carefully examined. The absorptive oxygen bond is about 50% of the total oxygen bond by using a semi-quantitative method. The value of actual stoichiometry δ′ is close to 2. The experimental results indicate that the thin films are of a cerium oxide-based solid solution with few oxygen vacancies in the lattice and many absorptive oxygen bonds at the surface. Week ferromagnetic behaviors were evidenced by observed M-H hysteresis loops at room temperature. Furthermore, an evidence of relative ferromagnetic contributions was revealed by the temperature dependence of magnetization. It is believed that the ferromagnetic contributions exhibited in the M-H loops originate from the absorptive oxygen on the surface rather than the oxygen vacancies in the lattice.
基金supported by the National Natural Science Foundation of China(Nos.52231007,51725101,11727807,51672050,52271167,61790581,22088101)the Ministry of Science and Technology of China(973 Project Nos.2021YFA1200600 and 2018YFA0209100)+3 种基金the Shanghai Excellent Academic Leaders Program(No.19XD1400400)Key Research Project of Zhejiang Lab(No.2021PE0AC02)the“Chenguang Program”by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.21CGA04)sponsored by Shanghai Sailing Program(No.21YF1401800).
文摘Stress induction plays a special role in performance control for material science.So far,it has remained challenging to systematically investigate magnetoelectric effect under stress-mediated interaction.Here we constructed a magnetoelectric device with piezoelectric stress induction,in which the stress plays a crucial intermediate role during the controllable modification of the magnetic behavior transitions under the magnetic field or current pulse driven process.The compressive stress was found to make the above process easier and reduce energy consumption via changing the magnetic domain energy state.Meanwhile,both the domain distribution and domain-wall driven process are sensitive to stress intensity.Our magnetoelectric device integrated the advantages of voltage-stress and spin-current for the control of magnetic behavior transition with the help of micro-nano processing.For the stress-induced magnetic behavior in magnetic materials was directly imaged and quantificationally investigated,the complex interactions between stress,magnetic domain motion,magnetic field,and spin current have been clarified.
文摘Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereformed, which are properly due to the existing of oxygen in the alloys introduced during the heat treatment process, the magnetic properties of the alloy decrease.
基金Supported by the National Natural Science Foundation of China(Nos.20901059 and 20771083)
文摘A novel diamagnetic-metal Cd（Ⅱ） complex with four nitroxide radicals[Cd（IM4Py）4Cl2]（IM4Py=2-（4＇-pyridinyl）-4,4,5,5-tetramethylimidazoline-1-oxyl） was synthesized and characterized by elemental analyses,IR spectra,UV-Vis spectra and X-ray single crystal diffraction.The complex crystallized in triclinic space group P1 with a=0.93285（14） nm,b=1.16827（18） nm,c=1.3660（2） nm,α=112.759（2）°,β=104.524（2）°,γ=92.008（3）°,V= 1.3143（3） nm3,Z=1,Dc=1.335 g/cm3,the final R1=0.0423 and wR2=0.1009.In the title complex,each Cd（Ⅱ） ion adopting a distorted octahedral geometry is coordinated by two Cl-anions and four pyridyl-N atoms from four IM4Py ligands.The magnetic measurements show the weak antiferromagnetic interactions between the nitroxide radicals.
文摘Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/α-Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at grain boundaries increases with increasing annealing temperature for the both types of magnets. The increase of this kind of defect can improve the coercivity of the single-phase magnet. Conversely,the increase of vacancy-cluster amount leads to decreasing of the coercivity for the nanocomposite magnet. It implies that the mechanism of dominant magnetic hardening for the two types of magnets is different, and the domain walls pinning mechanism in the single-phase magnet and the reversal magnetization nucleation mechanism in the nanocomposite magnet operate, respectively.
文摘Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin （2, 5/2） Ising system for the antiferromagnetic/antiferromagnetic （AFM/AFM） interactions on the bilayer square lattice under a time varying （sinusoidal） magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic （FM/FM） and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions.
文摘A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform electric field in a positive column of helium direct current(DC) gas discharge Graphs showing the electron density and energy distributions, and the percentage of electrons that reach the wall and the end of the positive column are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column which are in good agreement with experimental results.
文摘The nanocrystalline Fe-Ni-Cr coatings were electrodeposited by using the pulse current technique.The SEM results showed that the coatings had a mixed morphology of small nodules and fine cauliflower structures at low current densities.Also,the Cr content was increased at expense of Fe and Ni contents at high current densities.XRD patterns confirmed that the pulse current density had a positive effect on the grain refinement.The results of vibrating sample magnetometer(VSM)measurements demonstrated that by increasing the current density,the saturation magnetization was decreased and the coercivity was increased due to the enhancement of Cr content and the reduction of the grain size.The friction coefficient and wear rate values were decreased by increasing the pulse current density.Also,both the adhesive and abrasive wear mechanisms were observed on the worn surfaces.The abrasive grooves and the amount of wear debris were decreased by increasing the pulse current density.
基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2021L404)。
文摘A series of novel hexanuclear lanthanide dusters,namely,[Ln_(6)(HL)_(6)(NO_(3))_(6)]·3CH_(3)CN(Ln=Gd(1),Tb(2),Dy(3)and Er(4))was assembled using a multidentate ligand H3L(trolamine).The clusters 1-4 show a wheel-shaped Ln_(6)topology with the approximate diameter and thickness of 1.5 and 0.7 nm,respectively.All of them show high thermal stability.In the aspect of the catalytic capacities for the cycloaddition reactions of CO_(2)and epoxide,the reaction conditions,the substrate scope,and possible catalytic mechanism were investigated.The highest yield for clusters 1-4 is up to 99%at 333 K for 12 h.In particular,cluster 1 can be reused at least three times with no obvious loss of catalytic performance and keep the integrity of the crystal structure.Magnetic investigations reveal that cluster 1 exhibits a relatively large magnetocaloric effect with-ΔS_(m)=41.43 J/(kg·K)(T=3.0 K,7.0 T);while cluster 3 displays slow magnetic relaxation behavior under zero dc field with U_(eff)=0.51 K andτ_(0)=2.54×10^(-5)s.
基金the Materials Science Unit,Radiation Physics Department,National Center for Radiation Research and Technology,Egypt,for financing and supporting this study under the project Nanostructured Magnetic Materials。
文摘This paper addresses the manipulation of structural,morphology,optical and magnetic properties of LiCo0.25Zn0.25Fe2 O4 ferrite via incorporation of different proportions of La^3+at the expense of iron ions using a sol-gel method.The samples were characterized using the X-ray diffraction technique(XRD),Fourier transform infrared(FT-IR)spectroscopy,the energy dispersive X-ray spectra(EDX),inductively coupled plasma optical emission spectroscopy(ICP-OES),high resolution scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET)surface area analysis,ultraviolet-diffuse reflectance spectroscopy(UV-DRS),and vibrating sample magnetometer(VSM)technique.The Rietveld refinements of the samples indicate that at higher concentrations of La^3+,nanostructures with dual phase,i.e.cubic spinel and orthorhombic LaFeO3 perovskite with space group(Pbnm)appear.Optical studies show that the energy band gap(Eg)of the bare LiCo0.25Zn0.25Fe2 O4 ferrite sample(2.18 eV)reaches up to 2.47 eV at x=0.06 and above this concentration,it drops sharply to 2.00 eV.Although the saturation magnetization and the coercivity of LiCo0.25Zn0.25LaxFe2-xO4 are lower than that of LiCo0.25Zn0.25Fe2 O4 NPs.Overall,the superparamagnetic nature and low values of saturation magnetization and coercivity of LiCo0.25Zn0.25LaxFe2-xO4 NPs are suitable to be applied in transformers core.
基金supported by the National Natural Sci-ence Foundation of China under grant No. 50571003
文摘A new type of Ni-P alloy with rod-shape was prepared by electroless deposition method based on the shape of Nocadia, a kind of bacteria. The material was characterized by microbiological method, scanning electron microscope, energy dispersion spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction and vibrant sample magnetometer. It was found that Ni-P alloy deposited on Nocadia surface was amorphous when pH=8.0. The amount of Ni crystalline increased with pH of plating solution. Ni-P nano-particles deposited on active locations on the surface at the initial stage, and then homogeneous Ni-P film formed with time. Nocadia remained their original rod shape after Ni-P nano-particles deposition. The new type metal material formed of Ni-P alloy with nano-particles was prepared. The mag- netization of the material prepared at pH=9.7 is greater than that prepared at pH=8.0. The magnetic loss of the material prepared at pH=9.7 is less than 0.1. The dielectric loss exceeds 0.3 when frequency is higher than 14 GHz, which is 1.5 at 18 GHz. The new type Ni-P metal material with Nocadia shape has dielectric loss property.
