Pioneering insights into the superior performance of titanium as a fuel in energetic materials

In this work, for the first time, the spotlight was shined on in-depth understanding the reaction mechanism of nanoTi-based thermite. It was found that adding nanoTi into thermite can improve the combustion efficiency and lower the ignition temperature on Al based nanothermites. This experimental study aims at establishing the mechanisms driving this improvement by quantitatively analyzing the oxidation of Ti in contact with a strong oxidizer, such as CuO. Magnetron-sputtered CuO/Ti nanothermites were prepared, partially reacted and characterized using microscopy, differential scanning calorimetry, spectroscopy and X-ray diffractometric. Results show that similar to 70 % of heat of reaction of the Ti/CuO system is released within a single strong exotherm at 430 degrees C, thus confirming the early and fast Ti oxidation. High resolution electronic microscopy reveals that titania, terminal reaction oxide, is grown and propagates into the Ti layer, driven by the diffusion/reaction of oxygen atoms released by CuO at 300 degrees C. Spectroscopy measurements show that CuO/Ti redox reaction undergoes a two-step oxidation process: at 300 degrees C, Ti is first oxidized into TiO and further oxidized into crystalline TiO2 at 500 degrees C. This study confirms that Ti can be of great interest in addition or replacement of Al in nanothermites, for applications where it is desirable to lower the ignition temperature. Adding two CuO/Ti bilayers prior to the deposition of CuO/Al multilayers allows decreasing ignition time below the ms (200 mu s) against 15 ms without CuO/Ti. Also, a burn rate enhancement factor of x 3, and a reduction of the ignition delay by x 700 is obtained when replacing Al by Ti in standard CuO/Al multilayers.