COMBUSTION MODES IN THE TITANIUM-NITROGEN SYSTEM AT LOW NITROGEN PRESSURES

The macroscopic combustion regimes, as well as the dynamics of phase f ormation, for the titanium-nitrogen system at low nitrogen pressures ( 0.1 kPa < p < 50 kPa) have been studied. Several combustion modes, inc luding planar surface (high-temperature), surface spot, and planar lay er-by-layer (low-temperature) mode, have been observed. Also, a chaoti c spot mode was found at pressures below 2 kPa for conditions of high heat loss. Using the time-resolved x-ray diffraction method previously developed by the authors, it was shown in situ that different mechani sms of phase formation correspond to these combustion modes. For the h igh-temperature mode, titanium nitride appeared in the combustion fron t as the initial product. However, only solid solutions of nitrogen in titanium were formed during the low-temperature mode. A complex seque nce of phase formation was observed for spot combustion. (C) 1997 by T he Combustion Institute.