In situ electric field driven assembly to construct adaptive graded permittivity BaTiO3/epoxy resin composites for improved insulation performance

The applications of dielectric functionally graded materials in high-voltage systems have emerged as a potential strategy to obtain superior insulation performance in recent years. However, the existing preparation methods mainly rely on simple lamination or centrifugal force intervention, and cannot adapt to the complex electric field spatial distribution. In this work, we developed low partial discharge (PD), high flashover voltage barium titanate/epoxy resin (BT/ER) insulation composites with graded permittivity, which were assembled by the in situ electric field. Our approach involves (a) the migration and deposition of BT in high electric field strength regions, driven by in situ electrophoretic forces in the BT/ER suspension (dispensable), (b) the alignment of BT in high electric field strength regions, driven by in situ dielectrophoretic forces in the BT/ER suspension, and (c) the “freezing” of the composite structure by curing. The insulation performance of the samples after this electric field structuring was assessed by PD measurements and flashover tests. The PD of the samples with 2.0 vol% BT and electric field treatment was significantly reduced, and the flashover voltage was increased by 31.8% compared with the pure ER sample. Optical microscope images, scanning electron microscope (SEM) images and finite element simulations also verify that this type of electric field structuring can effectively reduce the electric field non-uniform coefficient. We believe that the strategy of electric field assembly to prepare graded permittivity materials (GPMs) is promising candidate for high performance insulation applications.