Carbon Hybrid Materials for Electromagnetic Interference (EMI) Shielding and Charge Storage Applications
Date
2019-04-01
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Abstract
Polymer nanocomposites having the combination of processability of the polymer matrix and versatility of the properties attainable using a large array of nanosized fillers have become the target of extensive studies for modern electronic applications. In this thesis, our attention was focused on two key advanced electrical applications of polymer nanocomposites namely, EMI (electromagnetic interference) shielding and charge storage. In EMI shielding, our goal was to alleviate the destructive interference of electronic devices caused by their emitted electromagnetic waves which adversely affect device functions as well as the performance of nearby devices. Another important aspect of EMI shielding is to protect humans from electromagnetic pollution which is responsible for many deleterious health effects. Charge storage applications are of great importance in designing embedded capacitors which is of the key challenges for the miniaturization of electronic circuits. In this thesis, we used carbon hybrid nanomaterials to prepare polymer nanocomposites for EMI shielding and charge storage applications. For EMI shielding part, we synthesized multi-wall carbon nanotubes by iron catalyst embedded in alumina substrate at five different synthesis temperatures (550°C-950°C (with 100°C intervals)) to have a clear image of how morphological changes of carbon nanotubes affected the final properties of polymer nanocomposites especially electrical properties and EMI shielding. The nanocomposites made with CNT synthesized at 650°C had significantly lower percolation threshold (around 0.4wt%) and higher electromagnetic interference shielding effectiveness (EMI SE) (20.3dB over the X-band for 3.5 wt% CNT and 1.1 mm thickness) than the other temperatures. High aspect ratio, high carbon yield and less defective structure of CNT synthesized at 650°C are the key ingredients of achieving high EMI shielding. For charge storage applications, we used two different strategies to fabricate high-k polymer nanocomposites. In the first strategy, we introduce MnO2 nanowires into PVDF/CNT polymer nanocomposites to interrupt the formation of a conductive network by CNTs which is responsible for the high loss of such systems. Our best result was achieved for CNT: MnO2NW (3.0:4.5wt%) hybrid nanocomposite with a high dielectric permittivity (50.6) and low dielectric loss (0.7), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). Finally, for the first time, we studied the charge storage properties of polymer nanocomposites contain new 2D materials called MXene and PVA as a polymer matrix. By implementing solution casting and vacuum-assisted filtration (VAF) flexible thin-films with exceptional dielectric properties (solution casting at10.0 wt% MXene: ε^'=370.5 ,tanδ=0.11 and VAF at10.0 wt% MXene: ε^'=3165.8 ,tanδ=0.1) were fabricated. The reported dielectric constants in this study are the highest values obtained with low dielectric losses for polymer nanocomposites in X-band frequency.
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Keywords
EMI shielding, Charge storage, MXene, CNT
Citation
Mirkhani, S. (2019). Carbon hybrid materials for electromagnetic interference (EMI) shielding and charge storage applications (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.