Toward homogenous AlN via reaction of Al nanoparticles with N₂ and NH₃: Reactive molecular dynamics simulation

Abstract

In this study, reactive molecular dynamics simulations were implemented to study the initial events in synthesizing AlN via aluminum nanoparticles (ANPs) with N2/NH3. The dissolution and diffusion behavior of N and H atoms in ANPs is elaborated. Without sufficient N2 supply and lower temperatures (below 2000 K), AlN nucleates and grows in an island shape, and the phase separation occurs through N atoms diffusion. The increase in N2 density accelerates the dissolution of N atoms through the nitride film to the core. In the NH3 atmosphere, H atoms generated by the cleavage of NH3 on ANPs surface dominate inward penetration, while N atoms are at a disadvantage in competition. ANPs have a large number of internal stress and form interwoven dislocations in the combustion. The number and distribution of dislocations are affected by temperatures and reaction time. ANPs not only expand in volume but also have local voids generated by hot spots at high temperatures. In the analysis of ANPs/NH3 species, the instability of the N‐H bond causes aluminum‐containing substances to spill out. Furthermore, N2 atmosphere together with a small amount of NH3 can loosen the nitride film and promote the diffusion of N atoms into the ANPs core. A homogeneous AlN could be tuned and fabricated under an optimal ratio of N2/NH3 (∼6:1).

Recent ReaxFF MD studies on pyrolysis and combustion mechanisms of aviation/aerospace fuels and energetic additives

“…Metals, especially aluminum, have high combustion enthalpy, which can increase the combustion temperature of the system, and aluminum combustion products are harmless and low cost, so they are widely used as fuel additives. An in-depth understanding of the pyrolysis or combustion of aluminum itself, [122][123][124][125][126][127][128][129] energetic materials/aluminum composites 112,[130][131][132][133][134][135] and small molecule/aluminum systems 123,134,[136][137][138][139][140] is of great interest.…”