DC conductivity characteristics of core-shell nanoparticles filled epoxy nanocomposites

Abstract

Epoxy-based nanocomposites are extensively used for High-Voltage Direct Current (HVDC) insulation. Incorporating inorganic nanoparticles can modulate interfacial traps, but the influence of core-shell architectures remains unclear. Here, we investigate field-dependent DC conductivity in epoxy composites filled with conventional SiO2, Al2O3, TiO2 and SiO2-coated core-shell counterparts (SiO2@SiO2, Al2O3@SiO2, TiO2@SiO2) filled with a total surface area of ≃ 5.82 m2. Samples were fabricated via shear mixing and cured at 80 ◦C (2 h) and 125 ◦C (3 h). J-E measurements (1–10 kV mm−1) were analysed using power-law and Poole-Frenkel/Schottky empirical fits. Currents were fit with stretched-exponential decay to extract
relaxation time (τ ) and stretch exponent (β). Conventional SiO2 and Al2O3 demonstrated sub-Ohmic low-field behaviour and higher transition fields, while TiO2 remained near-Ohmic. Core-shell composites demonstrated Ohmic drift in all cases and raised transition fields to 3.6-4.1 kV mm−1, with significantly accelerated de-trapping (τ ≃ 6.2-6.4 s, β ≃ 0.52-0.54). Findings demonstrate that silica shells result in homogeneous traps, extending the Ohmic regime and deferring space-charge-limited
conduction without compromising core-driven conductivity enhancement.

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Identifiers

ORCID for Sunny Chaudhary: orcid.org/0000-0003-2664-7083

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