Fabrication Of Zinc Oxide Nano/micro Structures And Their Application In Polymer-based Composites With High Dielectric Constant

Ever-increasing demand of higher density circuits in electronics hasgreatly accelerated the miniaturization and integration of chip electroniccomponents with high performance and multi-function, smaller size,higher efficiency and lower cost. Polymer based composites with highdielectric constant have gained increasing attention due to their easyprocessing and flexibility and wide application in embedded capacitors.Our interests are focused on the influence of polymer matrices and the sizeand shape of fillers on the whole dielectric performance of the resultingcomposites.Firstly, Zinc Oxide nanorods (around700nm), were used as dopant toprepare nanocomposites with poly(vinylidene fluoride)(PVDF) andpoly(methyl methacrylate)(PMMA). The structural and dielectricproperties of the resulting nanocomposites were revealed in dependence on the loading of ZnO nanorods and selection of polymer matrices. It wasconcluded that the polymer matrices play an important role in determiningthe dielectric constant of nanocomposites.To investigate the influence of ZnO nanorods on the structural anddielectric response of polymer nanocomposites, polymer nanocompositeswere then fabricated based on ZnO nanorods (around200nm) dispersed inPVDF-HFP. The morphology, crystalline structure and dielectric responseswere studied, and the resultant nanocomposites revealed a shift ofcrystalline structure and enhanced dielectric constant, which might beattributed to the change in polymer microstructure induced by thenanofillers as well as the interfacial effect.To further investigate the influence of shape and morphology of fillerson the overall dielectric properties of the resultant composites, twodifferent hierarchical ZnO structures were synthesized and utilized tofabricate polymer composites. Commercialized ZnO particles were alsoused to prepared composite, which was used as a counterpart.Comprehensive structural, morphological, thermal, and dielectric studieswere conducted on the resultant composites. The results of XRD, FTIR,DSC and DMA show that the impact of ZnO on the microstructure ofpolymer matrix is not sensitive to the morphology of fillers. It was found that hierarchical ZnO structures can bring a greater increase in dielectricconstant without sacrificing the breakdown strength compared to thecomposites with commercial ZnO fillers. The much higher dielectricconstant enhancement might be attributed to the ZnO percolation network.To gain a comprehensive knowledge of the influence of hierarchicalfillers on the structural and dielectric properties of the resultant composites,another hierarchical ZnO structure was synthesized and used as dopants toprepare polymer composites. A comprehensive study of the structural anddielectric response of the resultant composites was conducted. It was foundthat no percolation network was formed even when the loading of ZnOwas as high as50wt%. The dielectric relaxation behaviors of compositeswere also studied.