Study of surface-bulk mass transport and phase transformation in nano TiO2 using hyperfine interaction technique

TL;DR

This study investigates the phase transition from anatase to rutile in 70nm TiO2 crystallites using hyperfine interaction techniques, revealing the roles of surface-bulk mass transfer and annealing conditions.

Contribution

It provides new insights into the phase transformation mechanisms of nano TiO2, emphasizing the impact of annealing duration and temperature on phase stability.

Findings

Phase transition occurs at 823K with longer annealing.

Surface-bulk mass transfer influences phase transformation.

Crystallite growth correlates with annealing temperature.

Abstract

Phase transition from anatase to rutile for the 70nm TiO2 crystallite has been investigated by annealing at different temperatures followed by TDPAC measurement of these TiO2 crystallites adsorbed with 181Hf tracer. The width of the peaks in XRD spectra for TiO2 crystallites annealed at different temperatures indicates the growth of the crystallites with temperature. The samples annealed upto 823K for 4hrs showed no phase transition, except the growth of the crystallites. However, it showed phase transition at the same temperature (823K), when annealed for longer duration. Annealing for shorter duration at 1123K showed phase transition. 181Hf tracer adsorbed on 70 nm anatase TiO2 is found to be in different polymorphs (anatase & rutile) formed during annealing process. Surface to bulk mass-transfer is found to play a significant role in the phase transition process.