Description
TitleA micromechanics study on carbon-based and multiferroic composites
Date Created2016
Other Date2016-05 (degree)
Extent1 online resource (xviii, 141 p. : ill.)
DescriptionIn this thesis, two physical properties of modern composites are studied. One is the electrical conductivity of carbon nanotube- and graphene-based polymer nanocomposites, and the other is the magnetoelectric coupling of highly anisotropic piezoelectric-piezomagnetic multiferroic composites. Along the way, several related issues have also been examined. These include percolation threshold, interfacial resistance, electron tunneling, and filler agglomeration in the first case, and, in the second one, the influence of aspect ratio of inclusions, imperfect interface, and phase connectivity. The studies of these two problems are linked by the common theme of micromechanics theory but cast in different settings. The effective electrical conductivity and percolation threshold of CNT-based nanocomposites are investigated with the effective-medium approach as the backbone. We then introduce of a diminishing layer of interface with an interfacial resistivity that is further modified by Cauchy's statistical distribution function to account for the additional tunneling-assisted interfacial conductivity. The issue of filler agglomeration is examined in details for graphene-based nanocomposites, in which a two-scale effective-medium approach with graphene-rich and graphene-poor regions is also developed. Our predictions are shown to be in close agreement with experimental data. For multiferroic composites, our focus is on the intriguing property of magnetoelectric coupling coefficient which is absent in either piezoelectric or piezomagnetic phase but owned by overall composites. We study this iconic effect in depth for BaTiO3-CoFe2O4 system with different types of connectivity, including 1-3, 0-3, 2-2, that display the inclusion-matrix morphology, and 1-1, 0-0 connectivity that are marked by their symmetric geometrical footing. These two classes of composites are analyzed by the Mori-Tanaka method and the effective-medium approach, respectively. We demonstrate how the magnetoelectric coupling coefficients are highly dependent on the phase volume concentration, inclusion aspect ratio, interface effect, and phase connectivity. Our results also reveal that the magnetoelectric coupling of 0-0 connectivity are substantially higher than that of 0-3 connectivity, but the difference between 1-1 and 1-3 connectivity is limited. In the end, we point to the need of exploring the physical mechanism of interfacial resistance for carbon-based nanocomposites and the nonlinear coupling behaviors for ferroelectric-ferromagnetic composites in our future work.
NotePh.D.
NoteIncludes bibliographical references
Noteby Yang Wang
Genretheses, ETD doctoral
Languageeng
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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