Nacre-like mica makes top-shelf insulator

Abstract

Today’s power generators, transformers, and capacitors typically use paperlike sheets of the mineral mica for electrical insulation. Mica withstands high voltages and temperatures, but without additives that reduce its insulating ability, it is too brittle and weak for demanding applications—for example, in high-speed rail and aerospace—says Jianwei Wang of Hunan University. Wang and his team took inspiration from nacre, the exceptionally tough material that lines many mollusk shells, to make a better mica insulator (ACS Nano 2020, DOI: 10.1021/acsnano.9b07192). Nacre’s toughness comes from layers of calcium carbonate platelets embedded in an architecture of protein nanofibers. Wang’s team mimicked this structure using synthetic mica nanoplatelets and nanofibers of Kevlar 29. They prepared a hydrogel of these materials and dried it, making a paper about 25 µm thick. Compared with Nomex 818—a mica-and-Kevlar-based electrical insulating tape already used for high-voltage applications—the new material withstood a maximum voltage over five times as high,