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
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.
