In-situ assembling inorganic nanoparticles on the surface of aramid nanofibers for the enhanced mechanical and insulation performances of the prepared nanopapers

In this work, we used metal ions (Ca2+, Mg2+, and Al3+) to in situ assist the splitting of aramid fibers to prepare their nanofibers, which successfully grafted the CaCO3, Mg(OH)2, and Al(OH)3 nanoparticles (NPs) on the surface of aramid nanofibers (ANFs) since the alkaline environment. The nanopapers assembled from the inorganic NP modified ANFs show higher mechanical and insulation properties than the neat ANF film, as well as the thermal stability and water flux. The Mg2+ yielded sample shows increase of 66.2%, 151.3%, 332.6%, and 28.3% on stress, strain at break, toughness, and dielectric breakdown strength, respectively. The enhanced mechanical and insulation property is attributed to the structural densification and improved interfacial interactions, while the increased water flux is caused by the hydrophilicity of the inorganic NPs. After annealing at 400 °C for 2 h, the dielectric breakdown strength is further improved due to the dense microstructures, but the stress and elongation are decreased. This work provides a general strategy to construct zero-dimensional NPs on the surface of ANFs, which can effectively enrich their structures, properties, and applications without lowering other properties.