The interface between polymer and particle plays an important role in designing the polymer nanocomposite dielectrics. A bi-functional organophosphate coupling agent, aminoethylphosphate (AEP) was self-assembled on barium titanate (BT) nanoparticles to provide surface passivation, reduce surface conductivity, and assist dispersion within thermosetting epoxy polymer. In addition, the coupling agent covalently reacts with the polymer matrix upon curing to yield a stronger, covalent interface between particle and matrix. Impedance spectroscopy was employed as a novel approach for studying the dielectric nature of modified and unmodified nanoceramic particles suspended as a slurry within a suitable, Maxwell liquid, butoxyethanol (BOE). The particles' dielectric properties were then extracted from impedance spectra. Surface functionalization reduced the particles surface conductivity and improved the dielectric characteristics of nanoparticles. Nanodielectric composites were prepared with enhanced dielectric characteristics: native polymer glass transition temperature, reduced dielectric loss including Maxwell-Wagner relaxation at very low frequencies and reduced leakage current density, and improved dielectric breakdown resistance. Improvements were attributed to reduction in surface conductivity of the nanoparticles and a stronger, covalent interface. The energy storage density of the covalently bonded 5 vol.-% BT composite in epoxy (~3.6 J�cm-3) was more than twice that of the pure polymer dielectric film. A ~30�m film with 30 vol.-% of BT resulted in maximum energy storage density of ~10 J�cm-3 at dielectric breakdown field of ~275 V��m-1.

Study of nanoceramic-polymer, interfacially coupled nanodielectric composites

245th National Meeting (2013)

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