液相剝離法製備石墨烯奈米片應用於電磁波干擾屏蔽

Synthesis of Graphene Nanoplatelets via Liquid Phase Exfoliation for Electromagnetic Interference Shielding Applications

賀忻年(Hsi-Nien Ho)

指導教授 ： 劉偉仁

中原大學/工學院/化學工程研究所/碩士(2020年)

https://doi.org/10.6840/cycu202000424

摘要

本研究透過低溫高壓液相剝離技術來製備高品質寡層石墨烯，並探討三種石墨原料脫層前後對電磁波屏蔽的影響，此新穎技術可以連續大量生產石墨烯，且不需使用到強酸或強氧化劑。其中Mo-8μm石墨烯擁有最好的脫層效果，片徑為8.6 μm，平均厚度為2.5～3.5 nm，層數約7至10層，而此脫層技術也維持了石墨烯的結構使其擁有非常低的缺陷值，ID/IG僅0.092。將20 wt.%的Mo-8μm石墨烯與石蠟混合後量測其在X-band下的屏蔽效益達到19.28 dB，相較於8μm石墨原料提升了4.26 dB。接著我們透過奈米碳管的複合來提升材料的屏蔽效益，奈米碳管可以搭接在石墨烯層與層之間形成更緻密的導電網路，與5 wt.%奈米碳管複合時有最高的屏蔽效益24.2 dB。最後我們利用冷凍乾燥技術來減少石墨烯懸浮液在乾燥過程中的堆疊現象，Mo-8μm石墨烯(凍乾)的屏蔽效益達到39 dB。而Mo-8μm石墨烯(凍乾)與5 wt.%的奈米碳管複合後，其屏蔽效益更是高達52 dB。除了屏蔽效益外，我們也對石墨烯進行吸波的討論，將8.3 wt.%的石墨烯混入矽橡膠中並量測其在3～18 GHz頻段下的介電性質與反射損失，透過低溫高壓液相剝離技術結合冷凍乾燥技術使材料的介電性質與吸波能力顯著提升，厚度為2.2 mm的Mo-8μm石墨烯(凍乾)膠片有最佳吸波在7.04 GHz達到-40.46 dB。
本研究實現可連續式量產石墨烯並擁有優異的電磁波屏蔽與吸波能力，材料可以運用在5G通訊、國防科技與隱形戰機上，在市場上具有極大的應用潛力!

關鍵字

石墨烯 ； 低溫高壓脫層法 ； 奈米碳管 ； 電磁波屏蔽 ； 電磁波吸波

並列摘要

In this study, we develop a facile and fast approach for preparing few-layer graphene nanoplatelets with high-quality via a jet cavitation process. This is a green and scalable process, and it can manufacture the product without disperser. Through this novel technology, we can successfully prepare graphene nanoplatelets derived from different graphite raw materials. Among them, Mo-8μm graphene has the best exfoliation performance. The average lateral size is 8.6 μm and the average thickness is about 2.5 to 3.5 nm, indicating the number of layers is 7 to 10 layers. This exfoliation technology also maintains the structure of graphene, which leads to low defect, the ID/IG ratio is only 0.092. Furthermore, we mixed 20 wt.% of Mo-8μm graphene with paraffin wax to obtain EMI shielding material. The shielding effectiveness under X-band achieved 19.28 dB, which was 4.26 dB higher than 8μm graphite raw material. Then we combined graphene nanoplatelets with carbon nanotubes (CNTs) to improve the shielding effectiveness of the material. CNTs can bridge the gaps between graphene nanoplatelets which results in forming a denser electrical conductivity network. Graphene nanoplatelets with 5 wt.% CNTs had the highest enhancement, and the shielding effectiveness reached 24.2 dB. Finally, we introduced freeze-drying technology to inhibit the stacking phenomenon of graphene suspension during the drying process. The shielding effectiveness of freeze-dried Mo-8μm graphene significantly increased to 39 dB, and after combined with 5 wt.% CNTs, material exhibited excellent shielding effectiveness up to 52 dB. In addition to the shielding effectiveness, we also discussed the microwave absorption of graphene nanoplatelets. We mixed 8.3 wt.% of graphene nanoplatelets into silicone rubber and measured its dielectric properties and reflection loss in the frequency range of 3~18 GHz. Jet cavitation process combined with freeze-drying technology significantly improves the dielectric properties and absorption capabilities of the material. Freeze-dried Mo-8μm graphene film with a thickness of 2.2 mm achieved the best reflection loss of -40.46 dB at 7.04 GHz.
This study developed continuously scalable fabrication of graphene nanoplatelets and had excellent electromagnetic wave shielding and absorbing capabilities. The material can be used in 5G communications, defense technology and stealth fighters, and has great application potential in the market!

並列關鍵字

graphene ； jet cavitation ； carbon nanotubes ； electromagnetic interference shielding ； microwave absorption

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