Controlled formation of nanoparticles utilizing laser irradiation in a flame and their characteristics

Controlled synthesis of nanoparticles has been carried out using laser beam irradiation on aggregates forming in a flame. This coalescence enhanced method transforms titania aggregates into much smaller unagglomerate spherical anatase nanoparticles by reducing the characteristic time of coalescence of nanoparticles. These transformed nanoparticles exhibit not only better thermal stability, but also unusually small grain growth during a simple pressureless sintering, which ultimately lead to a full dense bulk ceramic with 60 nm grains. Such small grain size in full dense ceramics has not been achieved before without employing special sintering techniques. This would be attributed not only to the successful control of size and morphology of nanoparticles, but also to the synthesis of oxygen vacancy free particles, which was confirmed from Raman spectroscopy. (C) 2001 American Institute of Physics.