DC conduction in epoxy based nano- and mesocomposites

Various samples based on bisphenol-A type epoxy resin were prepared. Composites were produced containing various amounts of aluminum oxide, aluminum nitride and magnesium oxide, using ex-situ polymerization of surface functionalized particles. The average particle size of the used filler material ranged between 22 nm (magnesium oxide) and 60 nm (aluminum nitride). Synthesis of the samples is described in detail. The structure of these composites was thoroughly analyzed, using both scanning and transmission electron microscopy. A structural variance could be discerned due to the different filler loadings ranging from 0.5 to 5% per weight. The samples were divided into nano- and mesocomposites, according to the microscopic analysis results. Conduction current measurement was performed in a three-terminal cell by means of an electrometer. To obtain a clear view on the conduction mechanisms involved, dc poling field strengths between 1 and 5 kV/mm were applied. The changes of the dc conductivity in nanocomposites compared to the unfilled host material are shown.