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UBC Theses and Dissertations

Electromagnetic composite nanofibers Bayat, Masoumeh


Multifunctional composite nanofibers containing magnetite (Fe₃O₄) nanoparticles are developed in this work. The multifunctional composite nanofibers are proved to be electrically conductive and magnetically permeable. Polyacrylonitrile (PAN) is used as an appropriate polymer which is capable of being pyrolized to produce electrically conductive carbon nanofiber matrix. In order to develop magnetic nanofibers, various amounts of Fe₃O₄ nanoparticles ranging from 3 to 10wt.% are embedded in the PAN nanofiber matrix. In addition, the electromagnetic behaviour of nanocomposites made of two different sizes (GA:20-30nm and GB:10-20nm) of Fe₃O₄ nanoparticles is examined. Electrospun composite nanofibers are thermally treated at both 700°C and 900°C to produce electromagnetic carbon nanofiber composites. The composite nanofibers are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Raman spectroscopy, four-point probe and Superconducting Quantum Interference Device (SQUID). Electromagnetic Interference Shielding Effectiveness (EMI SE) of the pristine carbon nanofibers as well as electromagnetic composite nanofibers is examined using Vector Network Analyzer with Thru-Reflect-Line (TRL) calibration. Uniform nanofibers are obtained for all samples with choosing 10wt.% PAN concentration in Dimethylformamide (DMF) with larger fiber diameters for composite nanofibers as compared with pristine carbon nanofiber. The magnetic properties of Fe₃O₄ nanoparticles are successfully transferred into the as-spun Fe₃O₄/PAN composite nanofibrous structure. The electromagnetic properties of the composite materials are tuned by adjusting the amount and size of Fe₃O₄ nanoparticles in the matrix and carbonization process. By embedding 10wt.% of GA:20-30nm Fe₃O₄ nanoparticle, saturation magnetization (Ms) of 16emu/g is obtained with electrical conductivity of 9.2S/cm for composite nanofiber carbonized at 900°C. However, the Ms and electrical conductivity values respectively decrease to 9.0emu/g and 1.96S/cm for composite made of 10wt.% GB:10-20nm Fe₃O₄ nanoparticle carbonized at 900°C. The high surface area provided by the ultrafine fibrous structures, the flexibility and tuneable electromagnetic properties are expected to enable the expansion of the design options for a wide range of electronic devices such as sensors and actuators as well as Electromagnetic Interference Shielding Effectiveness (EMI SE). The electromagnetic composite nanofibers are demonstrated to act as strong electromagnetic interference shield of up to 70-80dB.

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Attribution-NonCommercial-NoDerivatives 4.0 International