Nanofibrous TiO2 produced using alternating field electrospinning of titanium alkoxide precursors: crystallization and phase development

Abstract

High-yield, free-surface alternating field electrospinning (AFES) was effectively used in the fabrication of titanium oxide nanofibrous materials from the precursors based on titanium alkoxide and a blend of polyvinylpyrrolidone and hydroxypropyl cellulose. The alkoxide/polymer mass ratio in the precursor solution has significant effects on the precursor fiber production rate as well as the structure of resulting TiO₂ nanofibers after thermal processing of precursor fibers at temperatures from 500 to 1000 °C. Within the range of tested process parameters, the best fiber production rate of ∼5.2 g h⁻¹ was achieved, in terms of the mass of crystallized TiO₂ nanofibers, with the precursor that corresponded to 1.5 : 1 TiO₂/polymer mass ratio. TiO₂ nanofibers produced by calcination at 500 °C for 3 h had 100–500 nm diameters and were composed of anatase (20–25 nm crystallite size) with rutile content 0.1–6.0 mol%, depending on the precursor composition. A considerable amount of anatase phase (up to 80 mol%) can be retained after thermal processing of TiO₂ nanofibers at 750 °C for 3 h. A nanofibrous material composed of smooth and long, predominantly monocrystalline rutile, fibrous segments was produced at 1000 °C from the precursor with 2.5 : 1 TiO₂/polymer mass ratio.