Our experiments showed that the combustion of an Al-Bi2O3 nanoparticle mixture generated the highest pressure pulse among common nanothermite reactions and can potentially be used as a nanoenergetic gas generator. The combustion front propagation velocity and rate of energy release increased by up to three orders of magnitude when the particle size was reduced to a nanosize range for both the aluminum and the oxidizer. We developed a novel one-step (metal nitrate-glycine) combustion synthesis of nanostructured amorphous-like and highly crystalline bismuth trioxide nanoparticles. The combustion synthesis was conducted using a solution of molten bismuth nitrate as an oxidizer and glycine as a fuel. The glycine was completely combusted during the thermal decomposition of the bismuth nitrate pentahydrate and generated a temperature front that propagated through the sample. Increasing the fuel concentration increased the maximum combustion temperature from 280 to 1200 degrees C and the Bi2O3 particle size from 20 to 100 nm. The oxidizer/fuel ratio had a strong impact on the bismuth trioxide particle crystallinity. At low temperature (280 degrees C), amorphous-like bismuth trioxide nanoparticles formed, while at T > or =370 degrees C the structures were crystalline. A peak pressure of approximately 12 MPa and a thermal front propagating velocity of approximately 2500 m s(-1) were achieved during the combustion of an Al-Bi2O3 mixture containing 80 wt% of the synthesized Bi2O3 crystalline nanoparticles (size: 40-50 nm).
Nanoenergetic gas‐generator (NGG) mixtures may have various potential military applications from aircraft fuels to rocket propellants, explosives, and primers. To find reactions generating the highest pressure peak, we studied eight nanoenergetic reactions. The Al/Bi2O3 reaction generated the highest pressure pulse among the eight thermite reactions. We developed a highly efficient, one step process for synthesis of Bi2O3 nanostructured particles. Its use generated about a three times higher peak pressure (∼10 MPa) than when using commercial bismuth oxide nanoparticles (3 MPa). The pressure in the vessel rose very rapidly to a peak value for a duration of ∼0.02 ms and ΔP/Δt of up to 500 GPa s−1. Increasing the crystallinity of the bismuth oxide nanoparticles increased the peak gas pressure by 25%. The maximum pressure×volume (PV) value obtained at m=0.1 g with our synthesized Bi2O3 was 707 Pa m3 much higher than that reported in the literature (33 Pa m3) for the same sample mass. Addition of carbon to the reactant mixtures did not increase the peak pressure. Addition of up to 3 wt.‐% of boron to the thermite systems increased the peak pressure by ∼50%.
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