Effect of vanadium ion implantation on the crystallization kinetics and phase transformation of electrospun TiO2 nanofibers

Abstract

The influence of V ion implantation on the thermal response of electrospun amorphous TiO2 nanofibers was studied with reference to structural phase transformation behavior, using in situ synchrotron radiation diffraction (SRD) measurements from room temperature to 1000 °C. Analysis of the SRD data provided activation energies for amorphous-to-crystalline TiO2 (anatase and rutile) and anatase-to-rutile transformations, and also assessments of the influence of V ion implantation on microstructure development during calcination using estimates of crystallite size and microstrain. Non-implanted nanofibers were initially amorphous, with crystalline anatase first appearing at 600 °C, followed by rutile at 700 °C. The corresponding activation energies were 69(17) kJ/mol for the amorphous-to-crystalline TiO2 transformation and 129(5) kJ/mol for the anatase-to-rutile transformation. V ion implantation resulted in a lowering of the temperature at which each crystalline phase first appeared, with both phases being initially observed at 500 °C and with the anatase-to-rutile transformation being accelerated relative to the non-implanted sample. The effect of V ion implantation is seen through the substantial reduction in activation energies, which are 25(3) kJ/mol for amorphous-to-crystalline TiO2 and 16(3) kJ/mol for anatase-to-rutile transformations.