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dc.contributor.authorKim, Philseoken_US
dc.date.accessioned2010-01-29T19:32:47Z
dc.date.available2010-01-29T19:32:47Z
dc.date.issued2008-11-17en_US
dc.identifier.urihttp://hdl.handle.net/1853/31651
dc.description.abstractPolymer/ceramic nanocomposites benefit by combining high permittivities (r) of metal oxide nanoparticles with high dielectric strength and excellent solution-processability of polymeric hosts. Simple mixing of nanoparticles and polymer generally results in poor quality materials due mainly to the agglomeration of nanoparticles and poor miscibility of nanoparticles in host materials. Surface modification of metal oxide nanoparticles with phosphonic acid-based ligands was found to afford a robust surface modification and improve the processablity and the quality of nanocomposites. The use of phosphonic-acid modified barium titanate (BaTiO₃) nanoparticles in dielectric nanocomposites dramatically improved the stability of the nanoparticle dispersion and the quality of the nanocomposites. Surface modification of BaTiO₃ nanoparticles allowed high quality nanocomposite thin films in ferroelectric polymer hosts such as poly(vinylidene fluoride-co-hexafluoropropylene) with large volume fractions (up to 50 vol. %), which exhibited a remarkable combination of a high permittvity (35 at 1 kHz) and a high breakdown strength (210 V/µm) leading to a maximum energy storage density of 6.1 J/cm³. The effect of nanoparticle volume fractions on the dielectric properties of this nanocomposite system was investigated and compared with theoretical models. At high volume fraction of nanoparticles, the porosity of the nanocomposites was found to have important role in the dielectric performance. A combined effective medium theory and finite difference simulation was used to model the dielectric properties of high volume fraction dielectric nanocomposites with porosity. These results provide a guideline to optimize the volume fractions of nanoparticles for maximum energy density. Nanocomposites based on phosphonic acid-modified BaTiO₃ nanoparticles can also be used as printable high permittivity dielectrics in organic electronics. High volume fractions (up to 37 vol. %) of phosphonic acid-modified BaTiO₃ nanoparticles dispersed in cross-linked poly(4-vinylphenol) allowed solution-processable high permittivity thin films with a large capacitance density (~50 nF/cm²) and a low leakage current (10 8 A/cm²) suitable as a gate insulator in organic field-effect transistors (OFETs). Pentacene-based OFETs using these nanocomposites showed a low threshold voltage (< -2.0 V) and a large on/off current ratio (Ion/off 104 ~ 106) due to the high capacitance density and low leakage current of the gate insulator.en_US
dc.publisherGeorgia Institute of Technologyen_US
dc.subjectBarium titanateen_US
dc.subjectDielectric nanocompositeen_US
dc.subjectPhosphonic aciden_US
dc.subjectSurface modificationen_US
dc.subjectEnergy storageen_US
dc.subject.lcshLigands (Biochemistry)
dc.subject.lcshDielectrics
dc.subject.lcshNanocomposites (Materials)
dc.subject.lcshCapacitors
dc.titleSurface modification of nanoparticles for polymer/ceramic nanocomposites and their applicationsen_US
dc.typeDissertationen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentChemistry and Biochemistryen_US
dc.description.advisorCommittee Chair: Perry, Joseph W.; Committee Member: Kippelen, Bernard; Committee Member: Lyon, L. Andrew; Committee Member: Marder, Seth R.; Committee Member: Whetten, Robert L.en_US


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