Surface engineering boron/graphite fluoride composite with enhanced ignition and combustion performances. (1st September 2022) - Wang, Jian
Highlights: Nano-Al and fluorographene (FG) were employed as coating agents of boron. The maximum heat release is 5.6 kJ/g, the minimum ignition delay time is 88 ms. The B/GF mass ratios is able to tune the ignition and combustion performances. Abstract: Boron (B) shows great potential applications in the military and aerospace industry due to its high calorific value. However, the reactivity is limited by the inert oxide layer (B2 O3 ) that covers the B particles. Herein, nano-Al, and Fluorographene (FG) are employed as coating materials to enhance the ignition and combustion efficiency of boron. When graphite fluoride (GF) was utilized as an oxidizer (the B/GF mass ratio is 1:9), the maximum heat release of B@nano-Al/GF (∼5.6 kJ/g) and B@FG/GF (∼5.4 kJ/g) were markedly higher than that of raw B/GF (∼2.5 kJ/g), ascribed to the self-activation effect of the coating layer. On this basis, the combustion experiments were performed and their performances were compared and studied. Specifically, the ignition delay time of B@nano-Al/GF and B@FG/GF was decreased to 320 ms 262 ms, respectively, compared with that of raw B/GF (380 ms) with 15 W laser power. This is consistent with the ignition burning test, where the B@6%nano-Al/GF and B@2%FG/GF have higher flame height than raw B/GF. However, the maximum pressure and pressurization rate decreased for B@6%nano-Al/GF and B@2%FG/GF because of the reduced amount of gas caused by decreased boron content. Additionally, the effects of the B/GF mass ratio (1:9, 2:8, 3:7, 4:6) on the combustion performances of composites were fully studied. The pressure output, combustion reaction, and ignition delay time are reduced with B/GF mass ratios increased. This work could provide a general approach to improve the ignition and combustion performance of boron.