Title

Novel high frequency electromagnetic shielding measurements within functional geometries using non-metal and fatigued conductors

Date of Award

2017

Degree Name

Ph.D. in Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Donald A. Klosterman

Abstract

The purpose of this research was to develop novel nanoparticle-enabled material shields and conductors for use in electrical coaxial cables, and to create appropriate methods to characterize their response to high frequency electromagnetic fields. In addition, techniques to distinguish the effects of mechanical degradation on electrical properties were developed. Traditional electrical measurements methods are ineffectual to such characterization due to limitations with frequency range, sample geometry, field impingement, and false assumptions of field coupling to non-metal center conductors. In this study, a reverberation chamber was used to develop a novel measurement method using conduction characterizations from a network analyzer. Samples were fatigued to identify the effects of heavy use and mechanical degradation on shielding effectiveness and system characterization, including impedance, voltage standing wave ratio, return loss, and insertion loss. The novel measurement of shielding effectiveness as well as system characterizations was used to determine the effect of material properties on cabling functionality, both electrical and mechanical and their inter-relationship.The results showed that the combination of carbon nanotube yarn center conductors and carbon nanotube tape shields led to more signal attenuation and therefore much higher characteristic impedance. Utilizing the novel method to measure the shielding effectiveness allowed for the incorporation of these differences in power transmission while simultaneously analyzing the immunity of the three-dimensional shield within a high frequency field. The carbon nanotube tape shields provided lightweight and efficient shielding at higher frequencies (towards 5 GHz) due to a decreasing skin depth at higher frequencies. A braid architecture, that which was incorporated in the silver coated copper clad steel shield, proved to withstand mechanical fatigue better, while the carbon nanotube helical tape began to stretch apart. This was because the braid better axially supported the load and began to tighten, reducing the size of apertures in many instances. Though it is possible for the conductivity of carbon nanotube bulk materials to improve due to fatigue or tension, no over-arching trends were observed to have an effect of shielding post fatigue.

Keywords

Shielding (Electricity) Fatigue Measurement, Carbon nanotubes Mechanical properties, Shielding (Electricity) Materials, Materials Science, Electromagnetics, Engineering, shielding effectiveness measurements, carbon nanotube coaxial cables, carbon nanotube transmission lines, coaxial cable measurements, cable shielding, carbon nanotube shielding, high frequency immunity

Rights Statement

Copyright 2017, author

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