High Electromagnetic Shielding of Multiwall Carbon Nanotube Composites Using Ionic Liquid Dispersant
In this study, a novel polyimide (PI) film, consisting of multiwall carbon nanotubes (MWCNTs) dispersed in an Ionic Liquid (IL), were demonstrated to be high shielding effectiveness (SE). The film was potentially useful for screening electromagnetic interference(EMI) in an optical transceiver module. The experimental results showed MWCNT-PI composite dispersed well in IL exhibits a high far-field SE of 38 ~ 45 dB within the frequency range of 1 ~ 3 GHz. It was also demonstrated the MWCNT-PI composite prepared with IL dispersed process have higher SE and lower weight percentage of MWCNTs than those with non-IL-dispersed process. Their intermolecular forces were carefully examined in order to understand dispersion mechanisms among MWCNTs. The aggregation phenomenon of MWCNTs was known, resulting from van der Waals forces. In our study, IL was employed to disperse MWCNTs. A proposal reason was that the attractive force between cation of the IL and £k electrons of MWCNTs is greater than the van der Waals forces among MWCNTs. From conductivity measurement, percolation threshold of the IL-dispersed MWCNT-PI composite was 5.2 wt%; percolation threshold of the non-IL-dispersed MWCNT-PI composite was 11.5 wt%. Given the lower percolation threshold ,we demonstrated the successful dispersion of MWCNT by adding IL. From the results of Raman spectrometer analyses, the IL dispersion was proved to be a physical interaction.
Furthermore, the IL-dispersed MWCNT-PI composite was used as package material in monopole antenna and got a near-field SE of 37dB within the frequency of 2.8 GHz. It implied that the IL-dispersed MWCNT-PI composite has an excellent EMI performance.The IL-dispersed MWCNT-PI composite is suitable for packaging low-cost and high-performance optical transceiver modules in the application of the fiber-to-the-home (FTTH) lightwave transmission systems.
Advisor:Yan-Kuin Su; Jiang-Jen Lin; Wood-Hi Cheng; Mei-Ying Chang; Chao-Yung Yeh
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:multiwall carbon nanotube ionic liquid
Date of Publication:07/15/2008