Sequential Infiltration Synthesis for High-Precision Fabrication of Applied Ceramic Fibers with Designed Nanostructures─Nanowires, Nanobelts, and Core–Shell Fibers

Inorganic nanofibers are advantageous materials in a variety of applications such as gas sensing and catalysis due to their 1D morphology, high surface area, and versatile properties. Here, we present a new approach for high-precision ceramic fiber fabrication of AlOx, ZnO, and AlOx-ZnO core–shell fibers, with programmable dimensions, morphology, and surface structure, through controlled growth of metal oxides within electrospun polymer fibers using sequential infiltration synthesis (SIS). Designed growth profiles within the fiber are achieved through controlled diffusion of the SIS gaseous precursors; moderate growth gradients lead to spherical fibers after polymer removal, while sharp growth gradients result in fiber buckling into nanobelt morphology. To move towards complex inorganic fiber architectures, we extend single-metal-oxide SIS into spatially controlled, multi-material SIS and demonstrate AlOx-ZnO core–shell fibers with tunable core and shell thicknesses. The core–shell fibers are fabricated in a single SIS process, where the location of each metal oxide is controlled by its diffusion time. This study opens up new possibilities for high-precision, complex architecture and composition ceramic fibers fabrication process.