Effects of humidity on titania-based polyvinylpyrolidone (PVP) electrospun fibers

Humidity effects on titania-based nanofibers were studied by electrospinning solutions of different weight percentages of titanium (IV) n-butoxide (TNBT) and polyvinylpyrolidone (PVP) in N,N-dimethylformamide (DMF). Ambient humidities during electrospinning were typically varied between 25 and 75% RH. XRD and SEM were used to examine crystallization and determine optimal conditions for fiber formation. A specific combination of solute concentration (45-55 wt%) and ambient humidity (25-60% RH) allowed fiber formation. Lower solute concentrations resulted in electrospraying while higher humidities induced excessive plasticization of the PVP. Using a heated target allowed fiber formation at higher humidities (>60%). Following electrospinning, slight degradation of the 60 wt% (but not the 50 wt%) TNBT microstructure was observed when stored for longer periods possibly due to higher moisture uptake in case of higher solids loading. Examination of the fibers following pyrolysis at 500 degrees C for 6 h in air revealed the presence of individual nanoscale crystallites that could potentially boost ionic and electronic diffusion in batteries and solar applications. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.