Synthesis of Ag@Al₂O₃ core-shell structure nanoparticles and their enhancement effect on dielectric properties for Ag@Al₂O₃/polyimide nanocomposites

Abstract

A novel core-shell structure Ag@Al₂O₃ nano-particles were synthesized and doped into polyimide as conductive fillers to prepare the composite films with high dielectric properties and low dielectric loss. The morphology and structures of the Ag@Al₂O₃ nano-particles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-visible spectroscopy. All the results proved that the Ag@Al₂O₃ nano-particles had a typical core-shell structure, for the Ag particles were coated by Al₂O₃ shell and the average sizes of Ag@Al₂O₃ particles were between 30 to 150 nm. The as-prepared Ag@Al₂O₃ nanoparticles were doped into the polyimide with different mass fractions to fabricate the Ag@Al₂O₃/PI composite films via in-situ polymerization process. SEM analysis of composite films showed that the Ag@Al₂O₃ nanoparticles homogeneously dispersed in polyimide matrix with nanoscale. As dielectric materials for electronic packaging systems, the Ag@Al₂O₃/PI composites exhibited appropriate mechanical properties and enhanced dielectric properties, including greatly enhanced dielectric constant and just a slight increase in dielectric loss. These improvements were attributed to the core-shell structure of fillers and their fine dispersion in the PI matrix.

Keywords

core-shell structure / polyimide / nanocomposites / dielectrics

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