纳米镍-铁合金/膨胀石墨复合材料的制备、表征及其电磁屏蔽性能

The composites with nano-particles of Ni-Fe alloys dispersed on the nano-layers of expanded graphite (EG) were prepared by the impregnation of EG with ethanol solutions of nickel and iron acetates， followed by drying and reduction in H₂. The square nano-particles of Ni-Fe alloys with particle sizes of mainly 20～40 nm were found to be well spread on the layers of EG. The alloy nano-particles exhibited high shielding effectiveness (SE) for electromagnetic radiations at low frequencies due to their high magnetic conductivity. Since EG is electronically conductive and displayed high SE at high frequencies， the composites exhibited good SE at wide range of frequencies. The electric and magnetic conductivities of the composites could be monitored through regulating the loadings of alloy nano-particles on EG， and it was found that the composites with 20%～40% of the alloys exhibited good SE. Specifically， the composite 27%Ni-3%Fe-EG showed the excellent SE from 66 to 110 dB at the frequencies from 300 kHz to 1.5 GHz.     

Electron beam forming system for irradiation of large diameter cylindrical products

The report describes electron beam electromagnetic forming system, which is destined for irradiation of cylindrical long goods, specifically for PE tubes 160 mm diameter. System consists of electromagnet, power supply units, beam distributions control units, etc. for use at an electron accelerator at 5 MeV and 50 kW. The particular geometry of the magnet poles and their mutual arrangement are creating an irradiation field that allows the electrons to irradiate the surface of the product close to 90°.     

Effect of nanoparticle network formation on electromagnetic properties and cell morphology of microcellular polymer nanocomposite foams

Adding high loadings of nanoparticles can remarkably alter the functionality of polymer nanocomposite foams. Therefore, this dramatic change was studied at the percolation threshold as a point to predict the properties of foamed nanocomposites using the viscoelastic characteristics of un-foamed ones. In this research, the effect of incorporating 10–40 wt% of ZnO nanoparticles on rheological properties of PS/ZnO samples was investigated. Then, these samples were foamed at processing temperatures of 80 and 120 °C to study morphology and electromagnetic properties. First, the rheological study showed that the storage modulus of nanocomposites increased significantly above 20 wt% of nanoparticles. A connected network of nanoparticles altered the microstructure of nanocomposite at this rheological percolation. The morphological results show a higher cell density for foamed samples above the rheological percolation. From electromagnetic properties, the effect of ZnO connected network is obvious on the absorption enhancement for 30 and 40 wt% and only for 40 wt% of ZnO at 80 and 120 °C, respectively. Therefore, the viscoelastic properties of samples are still dominant at the lower temperature, but the foam structure became more important at the higher temperatures. This shows that the role of the filler network faded at the higher temperature and electromagnetic properties were changed with the foam structure. The microstructure expansion results in the decrease of filler amount at a fixed volume of foams, so more filler fraction is required to form a connected network of nanoparticles.     

EMI shielding and dynamic mechanical analysis of graphene oxide-carbon nanotube-acrylonitrile butadiene styrene hybrid composites

Carbon nanomaterials such as carbon nanotubes (CNTs), graphene and their hybrid have been studied extensively. Despite having excellent properties of CNTs and graphene have not yet been fully realized in the polymer composites. During fabrication agglomeration of CNTs and restacking of graphene is a serious concern that results in the degradation of properties of nanomaterials into the final composites. To improve the dispersion of CNTs and restacking graphene, in the present research work, we focused on the hybridization of graphene oxide and CNTs. Multiwalled carbon nanotubes (MWCNTs), functionalized carbon nanotubes (FCNTs), and graphene oxide-carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites were prepared separately by vacuum filtration followed by hot compression molding. Further, dynamic mechanical analysis (DMA), and electromagnetic interference (EMI) shielding properties of ABS composites reinforced carbon nanofillers were investigated. The dynamic mechanical properties of polymers strongly depend on the adhesion of fillers and polymer, entanglement density of polymer chains in the presence of carbon fillers. The dynamic mechanical characteristics such as storage, loss modulus, and damping factor of prepared composites were significantly affected by the incorporation of MWCNTs, FCNTs, and GCNTs. Maximum EMI shielding effectiveness of −49.6 dB was achieved for GCNT-ABS composites which were highest compared to MWCNTs-ABS composites (−38.6 dB) and FCNTs-ABS composites (−36.7 dB) in the Ku band (12.4–18 GHz). These results depict the great potential of GCNTs-ABS composites to be used in various applications of efficient heat dissipative EMI shielding materials for electronic devices.     

屏蔽槽SOI高压器件新结构和耐压机理

提出具有屏蔽槽的SOI高压器件新结构和自适应界面电荷耐压模型.该结构在屏蔽槽内产生跟随漏极电压变化的界面电荷,此电荷使埋层介质的纵向电场增加,同时使顶层硅的纵向电场降低,并对表面电场进行调制,因此屏蔽了高电场对顶层硅的影响.借助二维器件仿真研究器件耐压和电场分布与结构参数的关系.结果表明,该结构使埋氧层的电场从传统的3Es升高到近600V/μm,突破了传统SOI器件埋氧层的耐压值,大大提高了SOI器件的击穿电压.     

电磁带隙结构的信号完整性分析

该文运用HFSS和S参数模型,分别从时域和频域的角度通过仿真实验研究和分析了电磁带隙(EBG)结构对信号传输特性的影响,研究表明EBG结构的周期性高阻平面导致了传输信号的反射与滤波,严重影响了信号传输质量。平面周期越小,影响越大。最后通过实验仿真和理论分析给出了EBG结构的应用规则。     

14 kHz～18 GHz夹网电磁屏蔽视窗的研制

通过分析、比较不同制作工艺、不同目数的屏蔽玻璃的屏蔽效能测试结果,并结合电磁屏蔽原理,研制出了全新的165目屏蔽网,它完全满足GJB5729--2006中B级标准值的要求,可应用于对低频指标有高标准要求的场合。     

开关电源输入EMI滤波器设计与仿真

开关电源中常用EMI滤波器抑制共模干扰和差模干扰。三端电容器在抑制开关电源高频干扰方面有良好性能。文中在开关电源一般性能EMI滤波器电路结构基础上,给出了使用三端电容器抑制高频噪声的滤波器结构。并使用PSpice软件对插入损耗进行仿真,给出了仿真结果。     

EMS测试系统中的主要设备选型

结合标准和实际测试对EMS测试设备的要求,分别对射频电磁场辐射抗抗度和传导骚扰抗扰度测试系统的主要设备技术指标要求和选型,进行了详细阐述和分析,为如何选择满足用户要求的测试系统提供参考。