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 TiO 2 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 TiO 2 (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 amorphousto-crystalline TiO 2 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 TiO 2 and 16(3) kJ/mol for anatase-to-rutile transformations.

Effect of pressure on TiO2 crystallization kinetics using in‐situ high‐temperature synchrotron radiation diffraction

“…To place the phase levels from the SRD measurements on an absolute scale, the method described by Albetran et al was used. In summary, the level of amorphous titania was estimated by analyzing the variation in the SRD pattern background at each temperature.…”

“…The phase transformation activation energies were estimated for the amorphous‐to‐anatase transformation from in‐situ SRD data analysis using a modified version of Matusita et al and the Arrhenius equations. These estimates were used to calculate average TiO 2 phase transformation activation energies …”

Effect of calcination on band gaps for electrospun titania nanofibers heated in air–argon mixtures

“…6 shows a plot of band gap versus argon content corresponding to the absorbance spectra in Fig. 5, and Table 2 lists the band gap values for each sample type, and also specifies the sample phase compositions [10,25,30]. Table 3 compares band gap results from this study with literature data for titania materials with different forms, mixtures and atmospheric treatment.…”

“…Using titania in an electrospun nanofiber form is attractive for photocatalysis applications since titania nanofibers have a high ratio of surface area to volume, which increase the decomposition rate of air and water pollutants and this allows for photocatalytic reactions to occur more rapidly on the photocatalyst surface [23][24][25][26][27][28][29][30].…”

Dynamic Diffraction Studies on the Crystallization, Phase Transformation, and Activation Energies in Anodized Titania Nanotubes

“…The residual values for the Topas refinements R wp and R exp were ~ 9 and 2, respectively. The goodness-of-fit, X 2 , ranged from 4 to 5, which indicates that the quality of the refinements was acceptable [ 30 , 31 , 32 , 36 ]. Figure 5 shows typical SRD Rietveld residual plots at 900 °C with goodness-of-fit values of 4.26 for this pattern.…”