Degree Type

Thesis

Date of Award

2012

Degree Name

Master of Science

Department

Materials Science and Engineering

First Advisor

Xiaoli Tan

Second Advisor

Nicola Bowler

Abstract

Two multifunctional cyanate ester based composites with nanofillers of core-shell microstructures were synthesized and investigated for dielectric, mechanical, and other particular properties for the application of multifunctional structural capacitors. The weight reduction and device integration in spacecraft can contribute to significant energy saving by employing multifunctional structural capacitors. Si nanoparticles/Bisphenol E cyanater ester (Si/BECy) nanocomposites show a significant increase in dielectric constant compared to neat BECy. A low dielectric loss tangent is still maintained in this system thanks to the core-shell (Si-SiO2) microstructure of Si particles. Incorporation of Si nanoparticles also results in a large increase in composite's storage modulus. Furthermore, the AC conductivity of the composite was observed to decrease under compressive mechanical stresses due to the piezoresistive effect of Si.

Agglomerates of Fe3O4 nanoparticles coated with SiO2 are synthesized and incorporated into BECy to obtain nanocomposites, revealing an enhanced dielectric constant and storage modulus, and a relatively low loss tangent over a wide frequency and temperature range similar to Si/BECy system. Therefore, these novel cyanate ester based nanocomposites simultaneously display mechanical load-carrying, electric energy-storing and other functional properties, promising for multifunctional devices, in this case, structural capacitors.

Copyright Owner

Weixing Sun

Language

en

File Format

application/pdf

File Size

63 pages

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