Electromagnetic Interference Shielding Composites

Abstract

In recent years, the extensive development of gigahertz electronic systems and telecommunication devices in civilian and military sectors has brought serious electromagnetic pollution to a level never attained before, which may both affect the operation of electronic devices and pose a health issue to general public. The novel and effective electromagnetic interference (EMI) shielding material solutions in a wide variety of applications are active quest. One of the major challenges facing the electromagnetic interference shielding is the relatively low shielding efficiency. The other is the high cost due to the complicated shielding material fabrication process. Designing and fabricating efficient EMI shielding material in a simple method is our goal. One mechanism of EMI shielding is reflection. To effectively reflect the incoming radiation, the shielding material must have mobile charge carriers (electrons or holes), which interact with the electromagnetic fields in the radiation. Absorption is another mechanism of EMI shielding. For absorption, a material must possess electric and/or magnetic dipoles that interact with electric and magnetic vectors of incident EM radiation. The electric and magnetic dipoles should be provided by materials with high values of dielectric constant and magnetic constant. From the material science point of view, the key solution is designing material with mobile charge carriers, high dielectric constant and magnetic constant. From the point of view of feasible mass production, simplified processes and easy scale-up are of great importance. In this dissertation, the design and preparation of controlled high aspect-ratio SiC nanofibers (SiCNFs) with high dielectric constant and the functionalities of SiCNFs/epoxy composites for electromagnetic interference shielding applications are presented. Based on innovative materials design and synergistic effect on the performance advancement, composites with unique structures, SiC core with carbon shell microfibers(C-SiC) are designed and produced targeting the electromagnetic interference shielding applications. In addition, new high entropy alloy AlCoCrFeNi for electromagnetic interference shielding will be demonstrated due to its electric and magnetic properties. Meanwhile the effect of x value on the geometry and physical properties in AlxCoCrFeNi series alloys will be investigated. The material preparation processes and their performance enhancement mechanisms will also be discussed.