Atomic‐Scale Interfacial Charge Trapping in Epoxy‐ Al ₂ O ₃ @GPTMS Nanocomposites Under Multifield Stress: Decoupling Covalent Bonding Effects via Multiscale Experiment‐ DFT Synergy

ABSTRACT Epoxy/alumina (Al ₂ O ₃ ) nanocomposites are critical for high‐voltage insulation under extreme thermal‐electrical stresses (140°C, 60 kV/mm); yet the atomic‐scale mechanisms of charge trapping remain elusive. To comprehensively understand the interfacial charge trapping mechanisms in epoxy/Al ₂ O ₃ @GPTMS nanocomposites, the space charge behavior of epoxy/Al ₂ O ₃ @GPTMS nanocomposites under simultaneous high electric field (up to 60 kV/mm) and elevated temperature (140°C) conditions was systematically investigated through pulsed electro‐acoustic (PEA) measurements and density functional theory (DFT) calculations. The synergistic experimental–theoretical framework reveals that 1 wt% Al ₂ O ₃ @GPTMS nanoparticles mitigate space charge tion in epoxy composites under 60 kV/mm at 140°C, reducing field distortion by 32% compared to neat epoxy (EP0) and demonstrating superior charge suppression capability under extreme conditions. This work provides the atomic‐scale evidence of silane‐Al ₂ O ₃ covalent bonding‐induced deep traps (1.46 eV), which alter HOMO‐LUMO gaps and Fermi level alignment with electrodes and stabilize the electronic density of states, with the Al ₂ O ₃ @GPTMS phase exhibiting localized electrostatic potential maxima (+4.28 eV) that create deep traps. The combined experimental and theoretical approach provides atomic‐scale insights into how nanofiller modification alters charge injection barriers and trap distributions, offering a fundamental framework for designing high‐performance nanodielectrics.