Minimum ignition temperature of nano and micro Ti powder clouds in the presence of inert nano TiO_2 powder

摘要

Minimum ignition temperature (MIT) of micro Ti powder increased gradually with increases in nano-sized TiO_2 employed as an inertant. Solid TiO_2 inertant significantly reduced ignition hazard of micro Ti powder in contact with hot surfaces. The MIT of nano Ti powder remained low (583 K), however, even with 90% TiO_2. The MIT of micro Ti powder, when mixed with nano Ti powder at concentrations as low as 10%, decreased so dramatically that its application as a solid fuel may be possible. A simple MIT model was proposed for aggregate particle size estimation and better understanding of the inerting effect of nano TiO_2 on MIT. Estimated particle size was 1.46-1.51 μm larger than that in the 20-L sphere due to poor dispersion in the BAM oven. Calculated MITs were lower than corresponding empirically determined values for micro Ti powder because nano-sized TiO_2 coated the micro Ti powder, thereby decreasing its reaction kinetics. In the case of nano Ti powder, nano-sized TiO_2 facilitated dispersion of nano Ti powder which resulted in a calculated MIT that was greater than the experimentally determined value.