Effects of ultrasonic processing on phase transition of flame-synthesized anatase TiO₂ nanoparticles

The effect of ultrasonic processing on the phase transformation of flame-synthesized anatase TiO₂ nanoparticles heated to the rutile phase was investigated. TiO₂ nanoparticles of various sizes were prepared using a coflow hydrogen diffusion flame and an ultrasonic processor. Smaller nanoparticles having a similar portion of anatase phase using the ultrasonic processor were produced. On the basis of scanning electron microscopy images and specific surface areas, we observed that smaller nanoparticles tended to be sintered more easily than larger nanoparticles. From X-ray diffraction analysis, we demonstrated that when heated, TiO₂ nanoparticles synthesized using the ultrasonic processor at 60% of its maximum amplitude were transformed from the anatase phase to the rutile phase more easily than those formed without or with the ultrasonic processor operated at 20% of its maximum amplitude.