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 °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.