Effects of electrostatic polarities on the morphology of electrospun oxide nanofibers: A case study on alumina-based nanofibers

Abstract

Oxide nanofibers are widely used in several applications, including thermal insulation, fuel cells, flexible sensors, and catalyst support. Fiber morphology significantly affects their application performance. In this work, alumina-based nanofibers were successfully prepared using a sol-gel combined with an electrospinning method. The electrostatic polarity effects on fiber morphology were investigated. When fibers were electrospun by negative polarity at elevated voltages, the fibers retained uniform and smooth morphology, with a slightly increased average diameter and diameter uniformity. In contrast, ultra-thin nanofibers were generated when electrospinning was done under positive polarity. The strong charge repulsion by the agminated cations in the precursor caused bifurcations, finally forming ultra-thin nanofibers. At increased voltages, the electrospun fibers with positive polarity exhibited a distinctly increased average diameter and decreased diameter uniformity. This was attributed to the increased fiber whip scope, increasingly robust nonaxisymmetric whip behaviors, and fiber bifurcation during the jet whipping process. The results showed that the electrostatic polarities can affect the morphology of oxide fibers. This study provides guidance to prepare oxide nanofibers with desired morphology and specific requirements.