Effects of electrospinning parameters on titanium dioxide nanofibers diameter and morphology: An investigation by Box–Wilson central composite design (CCD)

Abstract

TiO2 nanofibers were electrospinned by using Polyvinylpyrrolidone (PVP) and Titanium tetraisopropoxide (TTIP) precursors. The effective parameters in this method such as the PVP content, TTIP content, distance between needle and collector, applied voltage, feed rate and pH were optimized by using Central Composite Design method and statistical software package Minitab ver.14. The results show that the PVP and TTIP concentrations have a direct and pH has an indirect relationship with the fiber diameter. Results showed that the PVP concentration was the most significant parameter in the fiber diameter of electrospun TiO2 nanofibers, while TTIP content and pH value were the next important parameters respectively. The influence of these parameters on diameter and morphology of TiO2 nanofibers was studied via SEM analysis, i.e. raising the pH value from 2.3 to 4.6 lead to decrease of the fiber diameter from 718±76 to 256±39nm and increasing the bead percent from 4% to 18%. Based on response surface plots, optimum conditions (PVP content: 6.5wt.%, TTIP content: 5wt.%, pH:3.2, distance: 25cm, voltage: 18.4kV, flow rate: 0.7ml/h) for producing TiO2 nanofibers with minimum diameter and fewer beads was obtained. According to DTA result, the optimum nanofibers were calcined at ∼560 and ∼685°C for 2h under air atmosphere. XRD analysis revealed the formation of anatase and rutile TiO2 phases after heat treatment at these temperatures respectively. Moreover, SEM images revealed an average shrinkage of the fiber diameter up to 50% (50.1±18nm) in the calcined nanofibers.