Fabrication and characterization of neat and aluminium-doped titanium (IV) oxide fibers prepared by combined sol–gel and electrospinning techniques

Sol–gel and electrospinning techniques were incorporated to produce polyvinylpyrrolidone (PVP)/titanium (IV) oxide composite fibers from solutions containing PVP and titanium tetraisopropoxide, with or without aluminium nitrate as the source of aluminium dopant. Upon the calcination of the as-spun fibers, the neat and the aluminium-doped titania fibers were obtained. Increasing the calcination temperature resulted in the decrease in the fraction of anatase phase within the fibers, as well as the increase in titania crystallite sizes. The presence of aluminium dopant, however, was found to greatly affect both physical and chemical properties of the synthesized titania fibers. Aluminium nitrate accelerated condensation of titanium oxide species during the sol–gel process, which resulted in increased viscosity of the spinning solution and consequently affected the diameters of the as-spun fibers. Aluminium dopant also played the major roles in both regulating the nucleation rate during crystallization of titania and controlling the growth mechanism of titania crystallites. As a result, the aluminium dopant caused the crystallite size of titania to decrease and retarded phase transformation from anatase to rutile.