Herein,we attempted to prepare MoS2/Fe@Fe3O4 nanocomposites capable of strongly absorbing broadband incident electromagnetic(EM)radiation and probed the effects of their composition on complex permittivity and permeab...Herein,we attempted to prepare MoS2/Fe@Fe3O4 nanocomposites capable of strongly absorbing broadband incident electromagnetic(EM)radiation and probed the effects of their composition on complex permittivity and permeability at 2-18 GHz.Calculations of normal-incidence reflection losses(RLs)based on EM parameters revealed that the Fe@Fe3O4 to MoS2 mass ratio strongly influenced the absorption peak intensity and bandwidth.Specifically,an RL peak of-31.8 dB@l5.3 GHz and a bandwidth(RL<-lOdB)of4.8 GHz(13.2-18 GHz)were achieved at a thickness of 1.52 mm and a Fe@Fe3O4 to M0S2 mass ratio of 60:40.Further,RL and bandwidth were investigated for oblique incidence,in which case two kinds of EM waves(TE-electric field perpendicular to plane of incidence;TM-electric field in the plane of incidence)were considered.The absorption peaks of TE and TM waves did not exceed-2 0 dB when the incidence angle increased to 3 0,and the bandwidth(R L<-10 dB)reached 4.2 GHz(TE wave)and 4.0 GHz(TM wave)when this angle was further increased to 40.0°and 50.4,respectively.Finally,the mechanism of microwave absorption was discussed in detail.展开更多
The oriented(CoIr)_(100-x)P_x(P = B, Ni, and SiO_2) soft magnetic films are prepared. Their morphology is measured using transmission electron microscopy(TEM), and reveals that these films exhibit good crystallinity a...The oriented(CoIr)_(100-x)P_x(P = B, Ni, and SiO_2) soft magnetic films are prepared. Their morphology is measured using transmission electron microscopy(TEM), and reveals that these films exhibit good crystallinity and high degree of the c-axis orientation. The magnetic properties are thoroughly investigated as a function of doping x. Our results show that all of these films possess negative magnetocrystalline anisotropy as required by possible applications. Both the intrinsic and extrinsic contributions are considered to interpret the broadening of the ferromagnetic resonance spectral linewidth. The intrinsic Gilbert damping is identified as the main cause of the linewidth broadening, while the extrinsic part originating from inhomogeneities only plays a minor role. More interestingly, our results show that the damping constant can be controlled by using the doping method.展开更多
Ce_(2)Fe_(17)N_(3-δ)composites have always been focused on electromagnetic wave(EMW)absorbing field because of their high resonance frequency and magnetic loss.However,the issues of preparation cost and impedance mis...Ce_(2)Fe_(17)N_(3-δ)composites have always been focused on electromagnetic wave(EMW)absorbing field because of their high resonance frequency and magnetic loss.However,the issues of preparation cost and impedance mismatching still limit the industrial conversion and practical application of Ce_(2)Fe_(17)N_(3-δ)composites.In this work,the composites of Ce_(2)Fe_(17)N_(3-δ)with a phosphate insulation layer(Ce_(2)Fe_(17)N_(3-δ)@FePO_(4))were prepared by a newly-developed reduction-diffusion(R/D)and phosphating processes using CeO_(2) as raw mate rials,and their microwave absorption properties were investigated.The composite filled with 30 vol%of the Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) has a minimum reflection loss(RL)of-63 dB and an effective absorption bandwidth(EBW,RL<-10 dB)of 3.83 GHz at a thickness of 1.25 mm in the X-band,and the EBW reaches 5 GHz under 0.98 mm in the Ku-band.This study demonstrates that the Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) composite s with low cost and excellent microwave absorption properties have a significant potential for industrial production and practical applications.展开更多
Soft magnetic composites(SMCs)are effective as magnetic powder cores in an inductor.Due to high saturation magnetization,large magnetocrystalline anisotropy and high operating frequency of M(metal)-RE(rear earth)soft ...Soft magnetic composites(SMCs)are effective as magnetic powder cores in an inductor.Due to high saturation magnetization,large magnetocrystalline anisotropy and high operating frequency of M(metal)-RE(rear earth)soft magnetic composites,it is possible to miniaturize inductor cores by reducing total loss,especially eddy current loss and excess loss at high frequencies.In this article,the characteristics of Ce_(2)Fe_(17)N_(3)/α-Fe(CFN/F)loss per volume and effective permeability reaching a high frequency of 3 MHz are investigated.The biphase CFN/F composite exhibits a high permeability of 16 at 70 MHz,which is two times greater than that of pure Ce_(2)Fe_(17)N_(3)(CFN)powders.The total loss is as low as 545 mW/cm^(3)at 3 MHz and 6 mT.The direct current(DC)-bias properties have a percent of permeability exceeding 65% at H=7960 A/m.This phenomenon indicates that our material has a higher working frequency and lower core loss than other materials;the biphase CFN/F structure is a promising and efficient approach for developing the miniaturized radio frequency(RF)inductor core.展开更多
Transmission line theory uses the complex nature of permeability and permittivity of a conventional magnetic absorber to evaluate its absorption properties and mechanism. However, because there is no method to obtain ...Transmission line theory uses the complex nature of permeability and permittivity of a conventional magnetic absorber to evaluate its absorption properties and mechanism. However, because there is no method to obtain the electromagnetic parameters of a metamaterial-absorber integrated layer(composed of a medium layer and a periodic metal array), this theory is seldom used to study the absorption properties of the metamaterial absorber. We propose a symmetry model to achieve an equivalent complex permittivity and permeability model for the integrated layer, which can be combined with the transmission line theory to calculate metamaterial absorption properties. The calculation results derived from both the transmission line theory and the high-frequency structure simulator are in good agreement. This method will be beneficial in practical investigations of the absorption mechanism of a metamaterial absorber.展开更多
Machine knowledge refers to the knowledge contained in artificial intelligence.This article discusses how to acquire machine knowledge,with a particular focus on the acquisition of causal knowledge.The latter is the p...Machine knowledge refers to the knowledge contained in artificial intelligence.This article discusses how to acquire machine knowledge,with a particular focus on the acquisition of causal knowledge.The latter is the process of interpreting machine knowledge.Through the analysis of certain research methods in the fields of physics and artificial intelligence,we propose principles and models for interpreting machine knowledge,and discuss specific methods including the automation of the interpretation process and local linearization.展开更多
We present detailed investigations of structural and static/dynamic magnetic properties of hydrogenated hcp-Co_(80)^(57)Fe_(4)Ir_(16) soft magnetic thin films.Two different kinds of defects,i.e.,destructive and non-de...We present detailed investigations of structural and static/dynamic magnetic properties of hydrogenated hcp-Co_(80)^(57)Fe_(4)Ir_(16) soft magnetic thin films.Two different kinds of defects,i.e.,destructive and non-destructive,were demonstrated by controlling the negative bias voltage of the hydrogenation process.Our results show that the structure and magnetic properties of our sample can be tuned by the density of the induced defects.These results provide better understanding of the hydrogenation effect and thus can be used in the future for materials processing to meet the requirements of different devices.展开更多
Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterize...Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterized by element analysis, thermal analysis, UV, IR and H NMR spectra. Besides, relaxivity (R1) of Gd-complex has been determined by INVREC.Au program, using inversion recovery pulse sequences, R1=8.05 mmol ·L-1 · s-1. The acute toxicity of Gd-complex in animal has also been tested, and the median lethal dose (LD50) is equal to (468.2±30) mg/kg.展开更多
Intelligent machines are knowledge systems with unique knowledge structure and function.In this paper,we discuss issues including the characteristics and forms of machine knowledge,the relationship between knowledge a...Intelligent machines are knowledge systems with unique knowledge structure and function.In this paper,we discuss issues including the characteristics and forms of machine knowledge,the relationship between knowledge and human cognition,and the approach to acquire machine knowledge.These issues are of great significance to the development of artificial intelligence.展开更多
基金financially supported by the National Natural Science Foundations of China (Nos. 11574122 and 51731001)the Fundamental Research Funds for the Central Universities (No. lzujbky-2017-k20)
文摘Herein,we attempted to prepare MoS2/Fe@Fe3O4 nanocomposites capable of strongly absorbing broadband incident electromagnetic(EM)radiation and probed the effects of their composition on complex permittivity and permeability at 2-18 GHz.Calculations of normal-incidence reflection losses(RLs)based on EM parameters revealed that the Fe@Fe3O4 to MoS2 mass ratio strongly influenced the absorption peak intensity and bandwidth.Specifically,an RL peak of-31.8 dB@l5.3 GHz and a bandwidth(RL<-lOdB)of4.8 GHz(13.2-18 GHz)were achieved at a thickness of 1.52 mm and a Fe@Fe3O4 to M0S2 mass ratio of 60:40.Further,RL and bandwidth were investigated for oblique incidence,in which case two kinds of EM waves(TE-electric field perpendicular to plane of incidence;TM-electric field in the plane of incidence)were considered.The absorption peaks of TE and TM waves did not exceed-2 0 dB when the incidence angle increased to 3 0,and the bandwidth(R L<-10 dB)reached 4.2 GHz(TE wave)and 4.0 GHz(TM wave)when this angle was further increased to 40.0°and 50.4,respectively.Finally,the mechanism of microwave absorption was discussed in detail.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574122 and 11704167)the Fundamental Research Funds for the Central Universities,China(Grant Nos.lzujbky-2017-k20 and lzujbky-2017-31)
文摘The oriented(CoIr)_(100-x)P_x(P = B, Ni, and SiO_2) soft magnetic films are prepared. Their morphology is measured using transmission electron microscopy(TEM), and reveals that these films exhibit good crystallinity and high degree of the c-axis orientation. The magnetic properties are thoroughly investigated as a function of doping x. Our results show that all of these films possess negative magnetocrystalline anisotropy as required by possible applications. Both the intrinsic and extrinsic contributions are considered to interpret the broadening of the ferromagnetic resonance spectral linewidth. The intrinsic Gilbert damping is identified as the main cause of the linewidth broadening, while the extrinsic part originating from inhomogeneities only plays a minor role. More interestingly, our results show that the damping constant can be controlled by using the doping method.
基金Project supported by the National Key R&D Program of China (2021YFB3501302)the National Natural Science Foundation of China (51731001)the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization's Key Research and Development Projects。
文摘Ce_(2)Fe_(17)N_(3-δ)composites have always been focused on electromagnetic wave(EMW)absorbing field because of their high resonance frequency and magnetic loss.However,the issues of preparation cost and impedance mismatching still limit the industrial conversion and practical application of Ce_(2)Fe_(17)N_(3-δ)composites.In this work,the composites of Ce_(2)Fe_(17)N_(3-δ)with a phosphate insulation layer(Ce_(2)Fe_(17)N_(3-δ)@FePO_(4))were prepared by a newly-developed reduction-diffusion(R/D)and phosphating processes using CeO_(2) as raw mate rials,and their microwave absorption properties were investigated.The composite filled with 30 vol%of the Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) has a minimum reflection loss(RL)of-63 dB and an effective absorption bandwidth(EBW,RL<-10 dB)of 3.83 GHz at a thickness of 1.25 mm in the X-band,and the EBW reaches 5 GHz under 0.98 mm in the Ku-band.This study demonstrates that the Ce_(2)Fe_(17)N_(3-δ)@FePO_(4) composite s with low cost and excellent microwave absorption properties have a significant potential for industrial production and practical applications.
基金Project supported by the National Key R&D Program of China(2021YFB3501302)Joint Fund of Equipment Pre-Researchthe Ministry of Science and Technology of China(6141A02033242)。
文摘Soft magnetic composites(SMCs)are effective as magnetic powder cores in an inductor.Due to high saturation magnetization,large magnetocrystalline anisotropy and high operating frequency of M(metal)-RE(rear earth)soft magnetic composites,it is possible to miniaturize inductor cores by reducing total loss,especially eddy current loss and excess loss at high frequencies.In this article,the characteristics of Ce_(2)Fe_(17)N_(3)/α-Fe(CFN/F)loss per volume and effective permeability reaching a high frequency of 3 MHz are investigated.The biphase CFN/F composite exhibits a high permeability of 16 at 70 MHz,which is two times greater than that of pure Ce_(2)Fe_(17)N_(3)(CFN)powders.The total loss is as low as 545 mW/cm^(3)at 3 MHz and 6 mT.The direct current(DC)-bias properties have a percent of permeability exceeding 65% at H=7960 A/m.This phenomenon indicates that our material has a higher working frequency and lower core loss than other materials;the biphase CFN/F structure is a promising and efficient approach for developing the miniaturized radio frequency(RF)inductor core.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574122 and 51731001)the Fundamental Research Funds for the Central Universities,China(Grant No.kzujbky-2017-k20)the Innovation Special Zone of National Defence Science and Technology,China
文摘Transmission line theory uses the complex nature of permeability and permittivity of a conventional magnetic absorber to evaluate its absorption properties and mechanism. However, because there is no method to obtain the electromagnetic parameters of a metamaterial-absorber integrated layer(composed of a medium layer and a periodic metal array), this theory is seldom used to study the absorption properties of the metamaterial absorber. We propose a symmetry model to achieve an equivalent complex permittivity and permeability model for the integrated layer, which can be combined with the transmission line theory to calculate metamaterial absorption properties. The calculation results derived from both the transmission line theory and the high-frequency structure simulator are in good agreement. This method will be beneficial in practical investigations of the absorption mechanism of a metamaterial absorber.
文摘Machine knowledge refers to the knowledge contained in artificial intelligence.This article discusses how to acquire machine knowledge,with a particular focus on the acquisition of causal knowledge.The latter is the process of interpreting machine knowledge.Through the analysis of certain research methods in the fields of physics and artificial intelligence,we propose principles and models for interpreting machine knowledge,and discuss specific methods including the automation of the interpretation process and local linearization.
基金the National Natural Science Foundation of China(Grant Nos.11704167,11704317,and 11574122).
文摘We present detailed investigations of structural and static/dynamic magnetic properties of hydrogenated hcp-Co_(80)^(57)Fe_(4)Ir_(16) soft magnetic thin films.Two different kinds of defects,i.e.,destructive and non-destructive,were demonstrated by controlling the negative bias voltage of the hydrogenation process.Our results show that the structure and magnetic properties of our sample can be tuned by the density of the induced defects.These results provide better understanding of the hydrogenation effect and thus can be used in the future for materials processing to meet the requirements of different devices.
文摘Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterized by element analysis, thermal analysis, UV, IR and H NMR spectra. Besides, relaxivity (R1) of Gd-complex has been determined by INVREC.Au program, using inversion recovery pulse sequences, R1=8.05 mmol ·L-1 · s-1. The acute toxicity of Gd-complex in animal has also been tested, and the median lethal dose (LD50) is equal to (468.2±30) mg/kg.
文摘Intelligent machines are knowledge systems with unique knowledge structure and function.In this paper,we discuss issues including the characteristics and forms of machine knowledge,the relationship between knowledge and human cognition,and the approach to acquire machine knowledge.These issues are of great significance to the development of artificial intelligence.
