Spatiotemporal distribution of thermal plasma temperature and precursor formation in a torch during TiO2 nanopowder synthesis

摘要

The spatiotemporal distribution of Ti excitation temperature (T_(ex)~(Ti)) was determined from twodimensional optical emission spectroscopy (2D OES) during TiO_2 nanopowder synthesis using an inductively coupled thermal plasma (ICTP) torch. The Ti feedstock powder was injected intermittently into the ICTP torch to elucidate the evaporation of the feedstock and the formation of atomic vapour, precursor molecules, and particle nuclei dynamically. The spectroscopic observation results revealed that T_(ex)~(Ti) was estimated as 2500-4000 K around the central axis of the ICTP torch, and more than 4500 K in the off-axis region. In the on-axis region, TiO was detected with a high radiation intensity in the lower temperature region. These results showed that TiO molecules are formed only in the low temperature region around the central axis of the ICTP torch. In addition, TiO molecular density could be high, especially in the downstream region at the central axis of the ICTP torch.