Effects of nano-BiF3 on the thermal oxidation, ignition and combustion characteristics of micron-sized Al powder

Pure n-BiF 3 is facilely prepared and uniformly loaded around μ-Al. • The n-BiF 3 serves dual functions: etching Al 2 O 3 shell and engaging in thermite reaction. • The n-BiF 3 significantly enhances the thermal oxidation, electric ignition, and combustion characteristics of μ-Al. • The effects of n-BiF 3 as an additive is positively dosage-dependent (1 wt% ∼ 5 wt%). Micron-sized Al (μ-Al) features high energy density and low cost, yet its surface alumina (Al 2 O 3 ) passivation film drastically limits energy release. In this study, pure nano-BiF 3 (n-BiF 3 ) was prepared by a mild chemical precipitation method. Al-BiF 3 composite particles with different n-BiF 3 loading were prepared by ultrasonic dispersion and vacuum filtration, and further composited with CuO and NH 4 ClO 4 (AP) to construct energetic composites, so as to investigate their modification effect on μ-Al. Structural characterization indicates that n-BiF 3 can be uniformly loaded around the surface of μ-Al without obvious segregation. Thermal analysis shows that n-BiF 3 releases fluorine-containing substances at high temperatures to etch the Al 2 O 3 shell. Adding n-BiF 3 at mass fractions of 1 wt%, 3 wt% and 5 wt% significantly improves thermal oxidation activity and oxidation weight gain rate by 46.5% ∼ 127.0% relative to untreated Al. Ignition and combustion tests demonstrate that n-BiF 3 effectively shortens ignition delay by 9.2% ∼ 12.8% for Al/CuO systems and by 24.6% ∼ 33.7% for Al/AP systems, shortens combustion time, raises the pressurization rate by 110.0% ∼ 490.0% for Al/CuO systems and 66.7% ∼ 416.7% for Al/AP systems, elevates system peak pressure and combustion temperature, and suppresses particle agglomeration. The above results reveal that n-BiF 3 has dual functions of etching the oxide layer and engaging in the thermite reaction, and the effect is enhanced with the increasing addition amount. This study provides a new strategy and experimental basis for the efficient modification of μ-Al. Download: Download high-res image (525KB) Download: Download full-size image