As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,red...As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results.展开更多
1.IntroductionThe rhombohedral compoundSmFeN(x=1～3)is currently attractinginterest due to its promise as a new perma-nent magnet material.Its magnetic proper-ties have been investigated in details.TheSm-Fe-N material...1.IntroductionThe rhombohedral compoundSmFeN(x=1～3)is currently attractinginterest due to its promise as a new perma-nent magnet material.Its magnetic proper-ties have been investigated in details.TheSm-Fe-N materials with quite good mag-展开更多
The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a cos...The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a costeffective reduction-diffusion method.The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm_(2)Fe_(17).The effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated.Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles.By employing the strategy of adding 20 wt% of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm_(2)Fe_(17) particles that are well-dispersed,with an average size of 2.2 μm.Furthermore,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm_(2)Fe_(17)N_(3) material was successfully obtained.This study could be useful for the development of high-performance Sm_(2)Fe_(17)N_(3) magnetic materials utilizing reduction-diffusion technology.展开更多
SmFealloy is the intermediate material for the preparation of SmFeNx(x ≈ 3); thus, the synthesis of pure SmFemother alloy is the key to obtaining highperformance SmFeNx. Reduction-diffusion(R-D) is a cost-effective m...SmFealloy is the intermediate material for the preparation of SmFeNx(x ≈ 3); thus, the synthesis of pure SmFemother alloy is the key to obtaining highperformance SmFeNx. Reduction-diffusion(R-D) is a cost-effective method. In this study, the R-D process of synthesizing SmFewas analyzed by scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), and X-ray fluorescence(XRF). Furthermore, the influences of the tightness of compacted reactants, the compensation amount of SmO,and the particle size of Fe on the formation of SmFewere discussed from the aspects of the three raw materials.The results show that Sm reduced from SmOreacts with Fe particles to form intermetallic compound SmFedirectly in the R-D reaction process of preparing SmFe;the generation of Sm and its migration to the surface of Fe particles control the reaction rate; a proper tightness of compacted reactants is necessary for ensuring the purity of SmFeproduct; pure SmFecan be obtained when the compensation of SmOis 33 % of the stoichiometry; and the sufficiency of the reaction improves with the decrease in the size of Fe powders under the same reaction condition.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3501300)the National Natural Science Foundation of China(Grant No.51731001)the Fund from the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization’s Key Research and Development Projects。
文摘As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results.
文摘1.IntroductionThe rhombohedral compoundSmFeN(x=1～3)is currently attractinginterest due to its promise as a new perma-nent magnet material.Its magnetic proper-ties have been investigated in details.TheSm-Fe-N materials with quite good mag-
基金Project supported by the National Natural Science Foundation of China (52201199,52271161)the Program of Top Disciplines Construction in Beijing (PXM2019_014204_500031)。
文摘The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a costeffective reduction-diffusion method.The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm_(2)Fe_(17).The effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated.Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles.By employing the strategy of adding 20 wt% of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm_(2)Fe_(17) particles that are well-dispersed,with an average size of 2.2 μm.Furthermore,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm_(2)Fe_(17)N_(3) material was successfully obtained.This study could be useful for the development of high-performance Sm_(2)Fe_(17)N_(3) magnetic materials utilizing reduction-diffusion technology.
基金financially supported by the Natural Science Foundation of Zhejiang Province, China (No. Y406406)the Xinmiao Talent Project of Zhejiang Province, China (No. 2014R403057)
文摘SmFealloy is the intermediate material for the preparation of SmFeNx(x ≈ 3); thus, the synthesis of pure SmFemother alloy is the key to obtaining highperformance SmFeNx. Reduction-diffusion(R-D) is a cost-effective method. In this study, the R-D process of synthesizing SmFewas analyzed by scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), and X-ray fluorescence(XRF). Furthermore, the influences of the tightness of compacted reactants, the compensation amount of SmO,and the particle size of Fe on the formation of SmFewere discussed from the aspects of the three raw materials.The results show that Sm reduced from SmOreacts with Fe particles to form intermetallic compound SmFedirectly in the R-D reaction process of preparing SmFe;the generation of Sm and its migration to the surface of Fe particles control the reaction rate; a proper tightness of compacted reactants is necessary for ensuring the purity of SmFeproduct; pure SmFecan be obtained when the compensation of SmOis 33 % of the stoichiometry; and the sufficiency of the reaction improves with the decrease in the size of Fe powders under the same reaction condition.
