Magnetic shielding of grain-oriented silicon steel was investigated. Ball scribing with spacing of 2 to 16 mm was performed at peak flux densities of 8.0 mT to 1.3 T. Magnetic shielding efficiency was calculated, incl...Magnetic shielding of grain-oriented silicon steel was investigated. Ball scribing with spacing of 2 to 16 mm was performed at peak flux densities of 8.0 mT to 1.3 T. Magnetic shielding efficiency was calculated, including absorption, reflection and inner multi-reflection shielding efficiencies. Magnetic shielding efficiency （MSE） increase ratios after different scribing spacing were compared, and thickness requirement to achieve absorption shielding of 50 dB was also calculated. The results show that magnetic shielding efficiencies of C711 and H668 silicon steels increase by 4.79 and 3.15 dB respectively after scribing of 16 mm. Before scribing, shielding efficiency of H668 steel was higher than that of C711 steel, while after scribing, both absorption and shielding efficiency gaps were largely abridged between C711 and H668 steels. Plate thickness of C711 steel could be reduced from 3.18 mm without scribing to 2. 20 mm after scribing of 16 mm. There is no apparent thickness reduction at lower flux densities; while the peak flux density is above 0.3 T, the shielding effect becomes apparent, and the thickness could be reduced from 2.28 mm without scribing to 1.70 mm with scribing spacing of 16 ram. Magnetizing process and its effect on variation of magnetic shielding were also analyzed.展开更多
Electromagnetic absorption and electromagnetic interference(EMI)shielding materials,especially absorption-based EMI shielding materials,are urgently desired to eliminate increasingly serious electromagnetic radiation ...Electromagnetic absorption and electromagnetic interference(EMI)shielding materials,especially absorption-based EMI shielding materials,are urgently desired to eliminate increasingly serious electromagnetic radiation pollution.Metal carbides exhibit great promise in realizing excellent EMI shielding owing to their outstanding electrical conductivity.However,because of the same reason,the electromagnetic wave reflection from the metal carbide films is hardly diminished and thereby metal carbides cannot realize absorption-based EMI shielding.Herein,metal carbide/Ni hybrid nanostructures are designed to realize electromagnetic absorption and absorption-based EMI shielding.The hybrid nanostructures are prepared by in situ reduction of Ni on metal carbide nanosheets.The loading of Ni greatly increases the impedance matching and attenuation constants.Metal carbide/Ni hybrids achieve a reflection loss of−41.7 dB at 10.8 GHz with a thickness of 1.8 mm.An EMI shielding effectiveness larger than 60 dB is achieved in the whole X-band with a metal carbide/Ni hybrid film of 50μm.Particularly,the absorption contributes 98.9%of total EMI shielding effectiveness,indicating the absorption-based EMI shielding.In addition,the metal carbide/Ni hybrid film exhibits very good mechanical properties and long-term stability in water.Our findings are very important for the development of electromagnetic absorption and absorption-based EMI shielding materials.展开更多
The rapid development of microwave-terahertz frequency band technologies has created an urgent demand for broadband electromagnetic wave absorption materials.In this study,a heterostructured composite comprising mixed...The rapid development of microwave-terahertz frequency band technologies has created an urgent demand for broadband electromagnetic wave absorption materials.In this study,a heterostructured composite comprising mixed-phase 1T/2H-MoSe_(2)(002)and WO_(3)(200)nanosheets was constructed to realize efficient electromagnetic wave absorption and shielding across both microwave and terahertz frequency bands.In the microwave region,the 1T/2H-MoSe_(2)/WO_(3)absorber exhibits a minimum reflection loss of-66.62 dB at 14.98 GHz with a thickness of 1.77 mm,attributed to slow polarization relaxation induced by multiple interfaces and structural defects.In the terahertz range,the system delivers a dominant shielding effectiveness of 67.3 dB at 1.31 THz with a thickness of 2 mm.This performance arises from the precise alignment of the Fermi level of metallic 1T-MoSe_(2)with the conduction band of WO_(3)at the interface,enabling rapid electron injection into WO_(3)with oxygen vacancies via electrochromism.This process induces the transition from W(VI)–O to W(VI-)–O,thereby enhancing both electronic and ionic polarization losses.When incorporated into polyvinyl alcohol(PVA)and fabricated into films,the resulting 500-μm-thick(1T/2H-MoSe_(2))/WO_(3)/PVA composite film achieves a maximum shielding effectiveness of 71.51 dB in the 0.2–1.8 THz frequency range,demonstrating excellent practical applicability.展开更多
基金Item Sponsored by National Natural Science Foundation of China(51174057,51274062)National High Technology Research and Development Program of China(2012AA03A503)
文摘Magnetic shielding of grain-oriented silicon steel was investigated. Ball scribing with spacing of 2 to 16 mm was performed at peak flux densities of 8.0 mT to 1.3 T. Magnetic shielding efficiency was calculated, including absorption, reflection and inner multi-reflection shielding efficiencies. Magnetic shielding efficiency （MSE） increase ratios after different scribing spacing were compared, and thickness requirement to achieve absorption shielding of 50 dB was also calculated. The results show that magnetic shielding efficiencies of C711 and H668 silicon steels increase by 4.79 and 3.15 dB respectively after scribing of 16 mm. Before scribing, shielding efficiency of H668 steel was higher than that of C711 steel, while after scribing, both absorption and shielding efficiency gaps were largely abridged between C711 and H668 steels. Plate thickness of C711 steel could be reduced from 3.18 mm without scribing to 2. 20 mm after scribing of 16 mm. There is no apparent thickness reduction at lower flux densities; while the peak flux density is above 0.3 T, the shielding effect becomes apparent, and the thickness could be reduced from 2.28 mm without scribing to 1.70 mm with scribing spacing of 16 ram. Magnetizing process and its effect on variation of magnetic shielding were also analyzed.
基金National Natural Science Foundation of China(61775129)Fundamental Research Funds for Central Universities(GK201902001)+2 种基金Funded Projects for the Academic Leaders and Academic Backbones of Shaanxi Normal University(18QNGG008)Scientific and Technological Funds for Returned Overseas Students of Shaanxi Province(2018007)Shaanxi Sanqin Scholars Innovation Team。
文摘Electromagnetic absorption and electromagnetic interference(EMI)shielding materials,especially absorption-based EMI shielding materials,are urgently desired to eliminate increasingly serious electromagnetic radiation pollution.Metal carbides exhibit great promise in realizing excellent EMI shielding owing to their outstanding electrical conductivity.However,because of the same reason,the electromagnetic wave reflection from the metal carbide films is hardly diminished and thereby metal carbides cannot realize absorption-based EMI shielding.Herein,metal carbide/Ni hybrid nanostructures are designed to realize electromagnetic absorption and absorption-based EMI shielding.The hybrid nanostructures are prepared by in situ reduction of Ni on metal carbide nanosheets.The loading of Ni greatly increases the impedance matching and attenuation constants.Metal carbide/Ni hybrids achieve a reflection loss of−41.7 dB at 10.8 GHz with a thickness of 1.8 mm.An EMI shielding effectiveness larger than 60 dB is achieved in the whole X-band with a metal carbide/Ni hybrid film of 50μm.Particularly,the absorption contributes 98.9%of total EMI shielding effectiveness,indicating the absorption-based EMI shielding.In addition,the metal carbide/Ni hybrid film exhibits very good mechanical properties and long-term stability in water.Our findings are very important for the development of electromagnetic absorption and absorption-based EMI shielding materials.
基金supported by the National Key R&D Program of China(No.2021YFB2800700)the National Natural Science Foundation of China(No.12274210)Partial support is from NSF of Jiangsu Province(No.BK20243062).
文摘The rapid development of microwave-terahertz frequency band technologies has created an urgent demand for broadband electromagnetic wave absorption materials.In this study,a heterostructured composite comprising mixed-phase 1T/2H-MoSe_(2)(002)and WO_(3)(200)nanosheets was constructed to realize efficient electromagnetic wave absorption and shielding across both microwave and terahertz frequency bands.In the microwave region,the 1T/2H-MoSe_(2)/WO_(3)absorber exhibits a minimum reflection loss of-66.62 dB at 14.98 GHz with a thickness of 1.77 mm,attributed to slow polarization relaxation induced by multiple interfaces and structural defects.In the terahertz range,the system delivers a dominant shielding effectiveness of 67.3 dB at 1.31 THz with a thickness of 2 mm.This performance arises from the precise alignment of the Fermi level of metallic 1T-MoSe_(2)with the conduction band of WO_(3)at the interface,enabling rapid electron injection into WO_(3)with oxygen vacancies via electrochromism.This process induces the transition from W(VI)–O to W(VI-)–O,thereby enhancing both electronic and ionic polarization losses.When incorporated into polyvinyl alcohol(PVA)and fabricated into films,the resulting 500-μm-thick(1T/2H-MoSe_(2))/WO_(3)/PVA composite film achieves a maximum shielding effectiveness of 71.51 dB in the 0.2–1.8 THz frequency range,demonstrating excellent practical applicability.
