Flyback converters in consumer and commercial products must adhere to strict regulatory standards for conducted and radiated electromagnetic interference(EMI).Managing EMI has become increasingly complex in mod-ern po...Flyback converters in consumer and commercial products must adhere to strict regulatory standards for conducted and radiated electromagnetic interference(EMI).Managing EMI has become increasingly complex in mod-ern power electronics,particularly with the integration of high-speed wide bandgap(WBG)devices into compact sys-tem layouts.A review of established modeling techniques and mitigation strategies for conducted EMI is presented,fo-cusing on differential mode(DM)and common mode(CM)noise,alongside radiated EMI in flyback converters.The discussion encompasses solutions at both component-level design and converter system optimization.展开更多
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
The rapid development of modern 5G technology has significantly increased the demand for multifunctional electromagnetic interference(EMI)shielding and wave-absorbing materials.Hence,a densification strategy was propo...The rapid development of modern 5G technology has significantly increased the demand for multifunctional electromagnetic interference(EMI)shielding and wave-absorbing materials.Hence,a densification strategy was proposed to fabricate multifunctional rigid polyimide(PI)composite foam.As a result,the composite PI foam exhibits excellent mechanical properties,with tensile and bending strengths of 4.7 and 21.1 MPa,respectively.Moreover,the composite PI foam achieves a promising EMI shielding performance with a high absorption coefficient(A)of 0.71,coupled with an X-band(8.2–12.4 GHz)EMI rating of 44 dB(2 mm)due to its high conductivity(20.29 ms/mm).Satisfyingly,the composite PI foam also has an optimal reflection loss(RL)of up to−46.4 dB and an effective absorption bandwidth(EAB)(RL<−10 dB)that covers the entire X-band.Meanwhile,the fabricated foam demonstrates a Joule heating performance of 89.2°C under supply voltages(3–9 V)and rapid response time(within 20 s)for stable and reproducible performance in long-term cycling.This work provides a versatile strategy for the development of lightweight and high-strength materials for EMI shielding and microwave absorption,demonstrating great potential for aerospace,microelectronics,and energy conversion applications.展开更多
Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum...Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum-assisted filtration.Interestingly,within the polytetrafluoroethylene(PTFE)-carbon nanotube(CNT)-Fe_(3)O_(4)layer(FCFe),CNT nanofibers interweave with PTFE fibers to form a stable“silk-like”structure that effectively captures Fe_(3)O_(4)particles.By incorporating a highly conductive MXene layer,the FCFe/MXene(FCFe/M)membrane exhibits excellent electrical/thermal conductivity,mechanical properties,and flame retardancy.Impressively,benefiting from the rational regulation of component proportions and the design of a Janus structure,the FCFe/M membrane with a thickness of only 84.9μm delivers outstanding EMI shielding effectiveness of 44.56 dB in the X-band,with a normalized specific SE reaching 10,421.3 dB cm^(2)g^(-1),which is attributed to the“absorption-reflection-reabsorption”mechanism.Furthermore,the membrane demonstrates low-voltage-driven Joule heating and fast-response photothermal performance.Under the stimulation of a 3 V voltage and an optical power density of 320 mW cm^(-2),the surface temperatures of the FCFe/M membranes can reach up to 140.4 and 145.7℃,respectively.In brief,the FCFe/M membrane with anti-electromagnetic radiation and temperature regulation is an attractive candidate for the next generation of wearable electronics,EMI compatibility,visual heating,thermotherapy,and military and aerospace applications.展开更多
文摘Flyback converters in consumer and commercial products must adhere to strict regulatory standards for conducted and radiated electromagnetic interference(EMI).Managing EMI has become increasingly complex in mod-ern power electronics,particularly with the integration of high-speed wide bandgap(WBG)devices into compact sys-tem layouts.A review of established modeling techniques and mitigation strategies for conducted EMI is presented,fo-cusing on differential mode(DM)and common mode(CM)noise,alongside radiated EMI in flyback converters.The discussion encompasses solutions at both component-level design and converter system optimization.
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.
基金support from the Postgraduate Innovation Foundation of Xi'an Polytechnic University(No.chx2024034)the Natural Science Foundation of Shaanxi Province(No.2022JQ-362,2021JQ-677)the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.21JK20180911).
文摘The rapid development of modern 5G technology has significantly increased the demand for multifunctional electromagnetic interference(EMI)shielding and wave-absorbing materials.Hence,a densification strategy was proposed to fabricate multifunctional rigid polyimide(PI)composite foam.As a result,the composite PI foam exhibits excellent mechanical properties,with tensile and bending strengths of 4.7 and 21.1 MPa,respectively.Moreover,the composite PI foam achieves a promising EMI shielding performance with a high absorption coefficient(A)of 0.71,coupled with an X-band(8.2–12.4 GHz)EMI rating of 44 dB(2 mm)due to its high conductivity(20.29 ms/mm).Satisfyingly,the composite PI foam also has an optimal reflection loss(RL)of up to−46.4 dB and an effective absorption bandwidth(EAB)(RL<−10 dB)that covers the entire X-band.Meanwhile,the fabricated foam demonstrates a Joule heating performance of 89.2°C under supply voltages(3–9 V)and rapid response time(within 20 s)for stable and reproducible performance in long-term cycling.This work provides a versatile strategy for the development of lightweight and high-strength materials for EMI shielding and microwave absorption,demonstrating great potential for aerospace,microelectronics,and energy conversion applications.
基金support from the National Natural Science Foundation of China(NSFC,Grant No.52175341)Shandong Provincial Natural Science Foundation(Grant No.ZR2022JQ24)Funding Project of Jinan City’s New Twenty Items for Colleges and Universities(Grant No.202333038).
文摘Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum-assisted filtration.Interestingly,within the polytetrafluoroethylene(PTFE)-carbon nanotube(CNT)-Fe_(3)O_(4)layer(FCFe),CNT nanofibers interweave with PTFE fibers to form a stable“silk-like”structure that effectively captures Fe_(3)O_(4)particles.By incorporating a highly conductive MXene layer,the FCFe/MXene(FCFe/M)membrane exhibits excellent electrical/thermal conductivity,mechanical properties,and flame retardancy.Impressively,benefiting from the rational regulation of component proportions and the design of a Janus structure,the FCFe/M membrane with a thickness of only 84.9μm delivers outstanding EMI shielding effectiveness of 44.56 dB in the X-band,with a normalized specific SE reaching 10,421.3 dB cm^(2)g^(-1),which is attributed to the“absorption-reflection-reabsorption”mechanism.Furthermore,the membrane demonstrates low-voltage-driven Joule heating and fast-response photothermal performance.Under the stimulation of a 3 V voltage and an optical power density of 320 mW cm^(-2),the surface temperatures of the FCFe/M membranes can reach up to 140.4 and 145.7℃,respectively.In brief,the FCFe/M membrane with anti-electromagnetic radiation and temperature regulation is an attractive candidate for the next generation of wearable electronics,EMI compatibility,visual heating,thermotherapy,and military and aerospace applications.
