In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
电磁干扰(electro magnetic interference,EMI)滤波器是一种抑制电力电子系统中传导电磁干扰的重要手段,其中集成式EMI滤波器由于体积小、高频性能好等优点得到广泛关注。该文介绍了一种新型集成式母线型EMI滤波器,这种滤波器将传输线...电磁干扰(electro magnetic interference,EMI)滤波器是一种抑制电力电子系统中传导电磁干扰的重要手段,其中集成式EMI滤波器由于体积小、高频性能好等优点得到广泛关注。该文介绍了一种新型集成式母线型EMI滤波器,这种滤波器将传输线与滤波器相结合,通过金属导体的"集肤"与"邻近"效应对低频工作电流与高频噪声电流进行分离,并对噪声电流实现"反射"与"耗散"双重衰减。论文采用有限元法,综合考虑了母线型EMI滤波器"磁-热-流体"多物理耦合场特性,从材料选择、电气及结构参数设计、滤波性能分析、温升特性分析等方面对滤波器进行了系统性的设计,对滤波器镀层结构及厚度、滤波器最大工作电流密度等具有工程应用价值的参数进行了详细计算,并给出了参考数值。母线型EMI滤波器滤波测试效果及温升实验表明滤波器具有较好的滤波性能和较强的载流能力,具有进一步开发并实际应用的前景。展开更多
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
文摘电磁干扰(electro magnetic interference,EMI)滤波器是一种抑制电力电子系统中传导电磁干扰的重要手段,其中集成式EMI滤波器由于体积小、高频性能好等优点得到广泛关注。该文介绍了一种新型集成式母线型EMI滤波器,这种滤波器将传输线与滤波器相结合,通过金属导体的"集肤"与"邻近"效应对低频工作电流与高频噪声电流进行分离,并对噪声电流实现"反射"与"耗散"双重衰减。论文采用有限元法,综合考虑了母线型EMI滤波器"磁-热-流体"多物理耦合场特性,从材料选择、电气及结构参数设计、滤波性能分析、温升特性分析等方面对滤波器进行了系统性的设计,对滤波器镀层结构及厚度、滤波器最大工作电流密度等具有工程应用价值的参数进行了详细计算,并给出了参考数值。母线型EMI滤波器滤波测试效果及温升实验表明滤波器具有较好的滤波性能和较强的载流能力,具有进一步开发并实际应用的前景。
