Wet-Spinning of Continuous Montmorillonite-Graphene Fibers for Fire-Resistant Lightweight Conductors

All-inorganic fibers composed of neat 2D crystals possessing fascinating performance (e.g., alternately stacking layers, high mechanical strength, favorable electrical conductivity, and fire-resistance) are discussed in detail. We developed a wet-spinning assmebly strategy to achieve continuous all-inorganic fibers of montmorillonite (MMT) nanoplatelets by incorporation of a graphene oxide (GO) liquid crystal (LC) template at a rate of 9 cm/s, and the templating role of GO LC is confirmed by in situ confocal laser scanning microscopy and polarized optical microscopy inspections. After protofibers underwent thermal reduction, the obtained binary complex fibers composed of neat 2D crystals integrate the outstanding fire-retardance of MMT nanoplatelets and the excellent conductivity of graphene nanosheets. High-resolution transmission electron microscopy and scanning electron microscope observations reveal the microstructures of fibers with compactly stacking layers. MMT-graphene fibers show increaing tensile strengths (88-270 MPa) and electrical conductivities (130-10500 S/m) with increasing graphene fraction. MMT-graphene (10/90) fibers are used as fire-resistant (bearing temperature in air: 600-700 °C), lightweight (ρ < 1.62 g/cm(3)) conductors (conductivity: up to 1.04 × 10(4) S/m) in view of their superior performance in high-temperature air beyond commercial T700 carbon fibers. We attribute the fire-resistance of MMT-graphene fibers to the armor-like protection of MMT layers, which could shield graphene layers from the action of oxidative etching. The composite fibers worked well as fire-resistant conductors when being heated to glowing red by an alcohol lamp. Our GO LC-templating wet-spinning strategy may also inspire the continuous assembly of other layered crystals into high-performance composite fibers.