Enhancing Burning Rate of Ammonium Nitrate by Ammonia Borane: Mechanism from Reactive Molecular Dynamics Simulation

The development of ammonium nitrate (AN)/ammonia borane (AB) as a green propellant is crucial for their applicability in different engines. This study investigates the release patterns of small products, particularly nitrogen-containing molecules, during the initial pyrolysis of AN/AB at low and high pressures using ReaxFF MD simulations. Compared with pure AN, the addition of AB gives the hybrid system enhanced reactivity, leading to faster decomposition and higher energy release. The results show that the consumption of AN in the S₁₃ system (AB with a mass ratio of 12.6 %) is accelerated at 1.47 MPa. NO₂ and NO are produced through HNO₃ and NO₃. At 6.89 MPa, AN exhibits the fastest decomposition rate in the S₁₅ system. The high pressure enhances more reactions of NO with free radicals such as NH and accelerates the release of N₂. As the percentage content of AB increases to 15.3 %, more H₂O while more NO₂ is generated. The effect of AB on the generation of radicals such as H₂ and H, is analyzed. AB not only promotes the initial pyrolysis of AN but also accelerates the conversion of intermediates.