Combustion characteristics study of 90 wt% Al/B/Ti-KClO₄ loading nanothermites with high-speed videography and pyrometry

Nanoscale aluminum, boron and titanium are attractive fuels in the field of energetic materials, therefore understanding the combustion behavior of them is important for their practical application. KClO₄ is a strong oxidizer with high oxygen content. We use 3D printing for the preparation of 90 wt% loading of nanoscale aluminum, boron and titanium with KClO₄ and study their combustion characteristics with high-speed videography and pyrometry. Different combustion behaviors are observed among the three composites. For Al-KClO₄, molten Al droplets with Al₂O₃ cap form and combine before leaving the burning surface and smoke cloud from the oxidation of Al vapor is present around the burning particles. B-KClO₄ and Ti-KClO₄ have similar combustion behaviors as coral-shaped agglomerates form on their burning surfaces and spherical burning particles are rarely observed. The combustion behavior characteristics among these three composites are attributed to the melting and boiling point of these metals and their corresponding metal oxides. Three-color pyrometry is utilized to estimate the temperature of the burning particles and the result shows that temperature of molten Al body and Al₂O₃ cap are higher than the melting point of Al and Al₂O₃, respectively, but also lower than the boiling points of Al and Al₂O₃, respectively. Estimated temperature of agglomerates for B-KClO₄ is below but near the melting point of B and explains why the agglomerates are non-spherical. The estimated temperature of agglomerates for Ti-KClO₄ is higher than the melting point of both Ti and TiO₂, and given the agglomeration being non-spherical, Ti₂O₃ with higher melting point is probably present and dominating the shape of the agglomerates.