Decomposition and Ignition Characteristics of Titanium Hydride at High Heating Rates

Abstract

An experimental study was conducted to evaluate the decomposition, ignition, and combustion behavior of titanium hydride under high heating rate conditions. Samples were deposited on filaments, which were rapidly heated by joule heating under various conditions. Dehydrogenation experiments were conducted under vacuum conditions at heating rates of up to 4 × 10⁵ K/s. The results of these experiments suggest that, at high heating rates, the onset of dehydrogenation is limited by intraparticle diffusion. The ignition and combustion behavior was studied in air and for ambient pressures ranging from atmospheric up to 7 MPa in a windowed pressure vessel. Broadband light emission was used to quantify the ignition temperature. The experiments revealed that the ignition temperature decreased linearly with increasing pressure from approximately 1700 K to 1475 K. Comparison of the dehydrogenation temperatures to the ignition temperatures over the entire pressure range suggests that the onset of the dehydrogenation process is not likely to be affected by ambient pressure. Finally, observation of the steady state combustion process by high speed imaging and post mortem analysis revealed many similar combustion characteristics to pure titanium. Particle explosions were observed and quenched particles were found to consist of titanium, nitrogen, and oxygen.

Keywords:

• Decomposition
• Ignition
• TiH₂
• Titanium hydride

ACKNOWLEDGMENTS

This research effort was supported through the ILIR program at the Naval Surface Warfare Center–Indian Head Division (NSWC-IHD) and from the Army Research Office. The authors would specifically like to thank Dr. Al Stern.