Dissertation Defence: Asymmetric Rubber-based Nanocomposites for Absorption-dominant Electromagnetic Interference Shielding
October 16 at 9:00 am - 1:00 pm
Ali Dehghani, supervised by Dr. Mohammad Arjmand, will defend their dissertation titled “Asymmetric Rubber-based Nanocomposites for Absorption-dominant Electromagnetic Interference Shielding” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering.
An abstract for Ali Dehghani’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. This examination will be offered in hybrid format. Registration is not required to attend in person, but please email mohammad.arjmand@ubc.ca to receive the Zoom link for this exam.
Abstract
Electromagnetic interference (EMI) generated by modern electronics demands lightweight, flexible shielding materials that dissipate waves through absorption rather than reflection. Conventional metal shields predominantly reflect EMI, producing secondary electromagnetic pollution unsuitable for next-generation wearable systems. To address these challenges, this thesis develops a new class of asymmetric rubber-based nanocomposites through the systematic structural engineering of conductive carbon nanotubes (CNTs), magnetic metal-organic framework (MOF)-derived nanoparticles, multilayer architectures, electromagnetic gradients, and anisotropic porosity.
After establishing theoretical design principles for absorption-dominant shielding, carbonized CoFe- and Fe-based MOF nanoparticles are synthesized and incorporated into CNT/styrene-butadiene rubber (SBR) matrices to construct progressively complex structures. First, alternating gradient multilayer nanocomposites were developed. The optimized six-layer architecture achieved an EMI shielding effectiveness (SE) of 50 dB with an absorption power coefficient of 0.57, while demonstrating high mechanical flexibility (13 MPa tensile strength, 120% elongation at break), and stable Joule heating. Second, dual-gradient multilayers are engineered with opposing conductivity and magnetic gradients to optimize impedance continuity. This bi-gradient nanocomposite achieved a 54 dB SE and a 0.70 absorption power coefficient, alongside adaptive infrared camouflage, rapid electrothermal conversion, and robust mechanical properties. Finally, anisotropic gradient rubber foams are developed by integrating asymmetric porosity with these electromagnetic gradients to maximize internal attenuation. The resulting foam achieved a 54 dB SE with an exceptional 0.86 absorption coefficient (the highest absorption performance in this study) while adding reliable piezoresistive motion sensing and excellent compressive resilience.
Overall, this thesis establishes a comprehensive architecture-driven framework for designing absorption-dominant EMI shields. By linking nanoparticle selection, structural asymmetry, and through-thickness impedance engineering, the developed nanocomposites demonstrate that structural engineering enables the simultaneous realization of high EMI shielding, minimal reflection, mechanical robustness, electrothermal energy conversion, and motion sensing. These findings provide practical design principles for next-generation multifunctional electromagnetic protection materials.
