Toward homogenous AlN via reaction of Al nanoparticles with N-2 and NH3: Reactive molecular dynamics simulation

L Song and Z Mei and SY Xu and FQ Zhao and XH Ju, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 105, 1343-1357 (2022).

DOI: 10.1111/jace.18123

In this study, reactive molecular dynamics simulations were implemented to study the initial events in synthesizing AlN via aluminum nanoparticles (ANPs) with N-2/NH3. The dissolution and diffusion behavior of N and H atoms in ANPs is elaborated. Without sufficient N-2 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 N-2 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, N-2 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 N-2/NH3 (similar to 6:1).

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