The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of th...The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of the film to 1.36 T at 300 K and remains 0.938 T at 380 K.As the thickness of the Y spacer layer increases,Y participates in the formation of the main phase in the film,and further regulates the formation of La-B phases.The results of the first-order reversal curve(FORC)and micromagnetic fitting show that the coercivity of all the films is dominated by nucleation mechanism.The c-axis preferred orientation,good magnetic microstructure parameters and the largest dipole interaction enhance the coercivity.Therefore,the introduction of the Y spacer layer can be an effective way to improve the coercivity of La-Nd-Fe-B film over a wide temperature range of 150 K-380 K.展开更多
The experimental regularity and the mechanism of coercive force of metallic cobalt powders and WC Co mixture powders used for WC Co cemented carbides production were explored. The results show that the specific coer...The experimental regularity and the mechanism of coercive force of metallic cobalt powders and WC Co mixture powders used for WC Co cemented carbides production were explored. The results show that the specific coercive force H sc is a practical physical parameter which can show exactly the demagnetization characteristic of cobalt, and its magnitude is related to structure of cobalt. The H sc of WC Co mixture powders bears a simple positive going relation to Co content in them when the structure of cobalt is constant. It increases with fining and well distributing of cobalt particles in WC Co mixture powders due to the increase of the magnetic moment interaction of adjacent cobalt particles and the residual stress existing among powder particles by grinding.展开更多
The influence of γ-phase composition in WC-Co cemented carbides on its specific coercive force H_(sc) hasbeen studied by analysing the imitative alloys of γ-phase. The results show that the H_(sc) of γ-phase is low...The influence of γ-phase composition in WC-Co cemented carbides on its specific coercive force H_(sc) hasbeen studied by analysing the imitative alloys of γ-phase. The results show that the H_(sc) of γ-phase is lower thanthat of pure cobalt, because the solute W can raise γ-phase H_(sc) but the carbon exhibits more intense negativeeffect on H_(sc). The effect is enhanced with raising the C solubilities in γ-phase.展开更多
The magnetic properties and microstructure of diffusion annealed [Ta/Nd/NdFeB/Nd/Ta]thin films have been investigated. The films were deposited on Si substrate with various thickness ratio of Nd/NdFeB layer (R=0～3.3)...The magnetic properties and microstructure of diffusion annealed [Ta/Nd/NdFeB/Nd/Ta]thin films have been investigated. The films were deposited on Si substrate with various thickness ratio of Nd/NdFeB layer (R=0～3.3), then diffused and crystallized by annealing at 650℃ for 10 min. The film without Nd layer showed soft magnetic behavior and high content of a-Fe phase. The films with R > =1 showed good hard magnetic properties with the high coercivity of about 20 kOe.展开更多
NdFeB coercive powder can be obtained directely by hydrogen treated ahoy ingots, The magnetic properties of the powder are comparable with that made by rapidsolidified process.An appreciable coercivity created during ...NdFeB coercive powder can be obtained directely by hydrogen treated ahoy ingots, The magnetic properties of the powder are comparable with that made by rapidsolidified process.An appreciable coercivity created during hydrogen treatment is closely related to the refined crystal grains.展开更多
Ce_x(CoFe)_(3-x)O_4 ferrites with different contents of Ce have been prepared by wetchemical method. The phases, morphologies and magnetic properties of the products were studied.It has been found that the products we...Ce_x(CoFe)_(3-x)O_4 ferrites with different contents of Ce have been prepared by wetchemical method. The phases, morphologies and magnetic properties of the products were studied.It has been found that the products were a single phase with spinel structure and consisted of granular particles in most cases.The coercive force of the products increased with the increase of concentration of Ce￣(4+) in the reaction solution.On the other hand,if Ce￣(3+) and Ce(OH)_4 were present in the reaction solution,some rod-shape crystals in the products were observed, which causes a great increase in coercive force,and the optimum value was obtained when[Ce￣(3+)] was about 5% of the total([Ce￣(3+)]+[Ce￣(4+)]).展开更多
The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal he...The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal here means an ferromagnetic single crystal with the size which is smaller than L0, and L0 is the critical value of the size of single-domain particles at the external magnetic field intensity H =0.Also, the coercive strength H(Ls) relating to the size of microcrystal Ls is given and quantitatively evaluated with the material SmCo5 as an instance.It is thus concluded that if L0 ＞ Ls ＞ LC, the antimagnetization of microcrystal will be subjected to a multi-domain process just like the particles of a size greater than L0, only if Ls ＜ LC, the anti-magnetizaton will be carried on in accordance with the Stoner-Wohlforth mechanism( LC is the maximum size of microcrystal with MHcth ).It is suggested that the material RECo5 is available to make an advanced magnet with MHC = 2 K/Mc.展开更多
In this paper,we consider a new algorithm for a generalized system for relaxed coercive nonlinear inequalities involving three different operators in Hilbert spaces by the convergence of projection methods.Our results...In this paper,we consider a new algorithm for a generalized system for relaxed coercive nonlinear inequalities involving three different operators in Hilbert spaces by the convergence of projection methods.Our results include the previous results as special cases extend and improve the main results obtained by many others.展开更多
The effects of CeO_(2)doping on the magnetic properties and microstructure of 2:17 type SmCo magnets are studied.With the increase of CeO_(2)from 0 wt.%to 3 wt.%,the coercivity of the magnets increases from 22.22 kOe ...The effects of CeO_(2)doping on the magnetic properties and microstructure of 2:17 type SmCo magnets are studied.With the increase of CeO_(2)from 0 wt.%to 3 wt.%,the coercivity of the magnets increases from 22.22 kOe to over 29.37 kOe,which is an increase of more than 30%.When the doping content is lower than 1 wt.%,the remanence and magnetic energy product of the magnets remain almost constant.Both decrease sharply as the doping concentration further increases.After CeO_(2)doping,the oxide content in the magnet increases significantly and the Ce element is uniformly distributed in the magnet.Observing the magnetic domains reveals that doping with CeO_(2)can refine the magnetic domains and make the magnetic domain wall more stable,resulting in a significant increase in the coercivity of the magnets.展开更多
A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet wa...A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet was for the Pr_(65)Al_(15)Cu_(20)GBD magnet,from 16.38 kOe to 22.38 kOe.Microstructural investigations indicated that increase in the Al content in the diffusion source can form a continuous grain boundary(GB)phase,optimizing the microstructure to enhance the coercivity.The coercivity enhancement is mainly due to the formation of a continuous GB phase to separate the main phase grains.Exchange decoupling between the adjacent main phase grains is enhanced after the GBD process.Meanwhile,the introduction of Al can effectively promote the infiltration of Pr into the magnet,which increases the diffusion rate of rare-earth elements within a certain range.This work provides a feasible method to enhance coercivity and reduce the use of rare-earth resources by partial replacement of rare-earth elements with non-rare-earth elements in the diffusion source.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3500303)the National Natural Science Foundation of China(Grant Nos.52031014 and 51971219).
文摘The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of the film to 1.36 T at 300 K and remains 0.938 T at 380 K.As the thickness of the Y spacer layer increases,Y participates in the formation of the main phase in the film,and further regulates the formation of La-B phases.The results of the first-order reversal curve(FORC)and micromagnetic fitting show that the coercivity of all the films is dominated by nucleation mechanism.The c-axis preferred orientation,good magnetic microstructure parameters and the largest dipole interaction enhance the coercivity.Therefore,the introduction of the Y spacer layer can be an effective way to improve the coercivity of La-Nd-Fe-B film over a wide temperature range of 150 K-380 K.
文摘The experimental regularity and the mechanism of coercive force of metallic cobalt powders and WC Co mixture powders used for WC Co cemented carbides production were explored. The results show that the specific coercive force H sc is a practical physical parameter which can show exactly the demagnetization characteristic of cobalt, and its magnitude is related to structure of cobalt. The H sc of WC Co mixture powders bears a simple positive going relation to Co content in them when the structure of cobalt is constant. It increases with fining and well distributing of cobalt particles in WC Co mixture powders due to the increase of the magnetic moment interaction of adjacent cobalt particles and the residual stress existing among powder particles by grinding.
文摘The influence of γ-phase composition in WC-Co cemented carbides on its specific coercive force H_(sc) hasbeen studied by analysing the imitative alloys of γ-phase. The results show that the H_(sc) of γ-phase is lower thanthat of pure cobalt, because the solute W can raise γ-phase H_(sc) but the carbon exhibits more intense negativeeffect on H_(sc). The effect is enhanced with raising the C solubilities in γ-phase.
文摘The magnetic properties and microstructure of diffusion annealed [Ta/Nd/NdFeB/Nd/Ta]thin films have been investigated. The films were deposited on Si substrate with various thickness ratio of Nd/NdFeB layer (R=0～3.3), then diffused and crystallized by annealing at 650℃ for 10 min. The film without Nd layer showed soft magnetic behavior and high content of a-Fe phase. The films with R > =1 showed good hard magnetic properties with the high coercivity of about 20 kOe.
文摘NdFeB coercive powder can be obtained directely by hydrogen treated ahoy ingots, The magnetic properties of the powder are comparable with that made by rapidsolidified process.An appreciable coercivity created during hydrogen treatment is closely related to the refined crystal grains.
文摘Ce_x(CoFe)_(3-x)O_4 ferrites with different contents of Ce have been prepared by wetchemical method. The phases, morphologies and magnetic properties of the products were studied.It has been found that the products were a single phase with spinel structure and consisted of granular particles in most cases.The coercive force of the products increased with the increase of concentration of Ce￣(4+) in the reaction solution.On the other hand,if Ce￣(3+) and Ce(OH)_4 were present in the reaction solution,some rod-shape crystals in the products were observed, which causes a great increase in coercive force,and the optimum value was obtained when[Ce￣(3+)] was about 5% of the total([Ce￣(3+)]+[Ce￣(4+)]).
文摘The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal here means an ferromagnetic single crystal with the size which is smaller than L0, and L0 is the critical value of the size of single-domain particles at the external magnetic field intensity H =0.Also, the coercive strength H(Ls) relating to the size of microcrystal Ls is given and quantitatively evaluated with the material SmCo5 as an instance.It is thus concluded that if L0 ＞ Ls ＞ LC, the antimagnetization of microcrystal will be subjected to a multi-domain process just like the particles of a size greater than L0, only if Ls ＜ LC, the anti-magnetizaton will be carried on in accordance with the Stoner-Wohlforth mechanism( LC is the maximum size of microcrystal with MHcth ).It is suggested that the material RECo5 is available to make an advanced magnet with MHC = 2 K/Mc.
基金Supported by the NSF of Henan Province(092300410150)Supported by the NSF of Department Education of Henan Province(2009C110002)Supported by the Key Teacher Foundation of Huanghuai University
文摘In this paper,we consider a new algorithm for a generalized system for relaxed coercive nonlinear inequalities involving three different operators in Hilbert spaces by the convergence of projection methods.Our results include the previous results as special cases extend and improve the main results obtained by many others.
基金the National Key R&D Program of China(Grant No.2021YFB3503102)the Zhejiang Provincial Key R&D Program of China(Grant No.2021C01191)the Science and Technology Innovation 2025 Major Project of Ningbo(Grant No.2020Z037)。
文摘The effects of CeO_(2)doping on the magnetic properties and microstructure of 2:17 type SmCo magnets are studied.With the increase of CeO_(2)from 0 wt.%to 3 wt.%,the coercivity of the magnets increases from 22.22 kOe to over 29.37 kOe,which is an increase of more than 30%.When the doping content is lower than 1 wt.%,the remanence and magnetic energy product of the magnets remain almost constant.Both decrease sharply as the doping concentration further increases.After CeO_(2)doping,the oxide content in the magnet increases significantly and the Ce element is uniformly distributed in the magnet.Observing the magnetic domains reveals that doping with CeO_(2)can refine the magnetic domains and make the magnetic domain wall more stable,resulting in a significant increase in the coercivity of the magnets.
基金Project supported by the National Key Research and Development Program of China (Grant No.2021YFB3502802)Major Science and Technology Research and Development Project of Jiangxi Province,China (Grant No.20203ABC28W006)+2 种基金the Key Research and Development Program of Shandong Province,China (Grant No.2019JZZY010321)Major Project of“Science and Technology Innovation 2025”in Ningbo City (Grant No.2020Z046)the K.C.Wong Magna Fund in Ningbo University。
文摘A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet was for the Pr_(65)Al_(15)Cu_(20)GBD magnet,from 16.38 kOe to 22.38 kOe.Microstructural investigations indicated that increase in the Al content in the diffusion source can form a continuous grain boundary(GB)phase,optimizing the microstructure to enhance the coercivity.The coercivity enhancement is mainly due to the formation of a continuous GB phase to separate the main phase grains.Exchange decoupling between the adjacent main phase grains is enhanced after the GBD process.Meanwhile,the introduction of Al can effectively promote the infiltration of Pr into the magnet,which increases the diffusion rate of rare-earth elements within a certain range.This work provides a feasible method to enhance coercivity and reduce the use of rare-earth resources by partial replacement of rare-earth elements with non-rare-earth elements in the diffusion source.
