| The rapid development of modern electronic technology provides great convenience to our life,however, it also brings about serious electromagnetic pollution, which would not only cause harm tothe health of human body, but also pose great threat to the information security of the equipment itselfand the stability of surrounding electronic equipment systems. Development and application ofhigh-performance electromagnetic shielding materials is an effective way to solve these problems.What is more, in order to adapt to the development trend of light-weight and highly integratedelectronic equipments in the future, electromagnetic shielding materials with light-weight andgas-permeable properties have become a new research hotspot. Based on the above introduction, inthis study, we have prepared a variety of electromagnetic shielding materials with foam structure andanalyzed their shielding performance and mechanism. The main contents of the study are as follows:(1) We have prepared three kinds of electromagnetic shielding materials (foam copper, foamnickel and foam copper-nickel alloy) by the electrophoretic deposition method and characterized theirmorphology, composition, mechanics and electromagnetic shielding performance. The results showthat the above three shielding materials all have the typical three-dimensional hollow mesh skeletonstructure, lightweight as well as good mechanical properties. Within the8-12GHz, the three kinds ofmaterials act their main shielding mechanism by absorbing losses. Under the same test condition, thefoam nickel material shows higher electromagnetic shielding effectiveness than foam copper. Thefoam copper-nickel’s electromagnetic shielding effectiveness is the best among the three, which canbe up to37dB and reaches the standard for civil use.(2) Various foam metal-carbon composite materials were prepared by a simple and effectiveelectrophoresis method and the electrophoretic parameters were discussed in detail. Under the bestelectrophoresis condition, we explored the effects of different carbon materials in improving theelectromagnetic shielding performance of different types of foam metals. The results indicate that thecomposite materials can also preserve the opening skeleton structure of the foam metal, lightweightand air permeable. Within8-12GHz, graphene and carbon nanotubes all can certainly enhance theelectromagnetic shielding performance of both magnetic foam nickel and diamagnetic foam copper,and graphene is more prominent than carbon nanotubes. Meanwhile, compared with magnetic foamnickel, graphene and carbon nanotubes have better improvement effect on the electromagneticshielding performance of conductive foam copper, which reflects the interface wave impedance mismatch difference of two kinds of carbon materials with different foam metal bases. Based on theabove, we continued to study the electromagnetic shielding performance of the foamcopper-nickel-grapheme three-layer composite material. It turns out that the multiple-layer compositeelectromagnetic shielding material can display a good synergistic shielding effect, within the sameband, the best effectiveness of the materials can be up to57dB, which is close to the militarystandard.(3) With the sacrifice temple of foam nickel, we further prepared graphene-polymethylmethacrylate composite foam electromagnetic shielding material by electrophoresismethod. Graphene is interconnected to form the three-dimensional conductive network in polymerskeletons to improve the electrical conductivity and thermal stability of the polymer substrate. Theelectromagnetic shielding tests show that this composite material also act its main shieldingmechanism by absorbing losses within8-12GHz and the electromagnetic shielding effectiveness canbe up to a maximum of12.7dB, what is more, the specific shielding effectiveness of this composite isas high as128.6dB·cm3·g-1, indicating it is a kind of promising ultralight electromagnetic shieldingmaterial. |
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