Molecular Dynamics Study on the Capture of Aluminum Particles by Carbon Fibers during the Propagation of Aluminum-Based Energetics

Previous experimental results have shown that carbon fibers (CF) can significantly promote the propagation of aluminum-based nanothermites and propellants. To explore the mechanism of this enhancement, the interaction of 4–6 nm Al/Al2O3 core–shell nanoparticles with a carbon fiber surface at 1000–2500 K is investigated by reactive molecular dynamics. The results show that regardless of the temperature, Al nanoparticles adhere to the surface of the carbon fiber upon interception. At 1000 K, Al nanoparticles adhere through physisorption; however, with increasing temperature, a transition to chemical bonding occurs, marked by the formation of Al–C bonds and the enhanced binding energy between the particle and the surface. The binding energy at 2500 K is 2 orders of magnitude higher than that at 1000 K. Larger Al particles are found to have a stronger binding energy at the same temperature. The sintering of two Al nanoparticles on the surface of the carbon fiber is also examined. Al nanoparticles that are bound to a carbon fiber surface have much lower sintering rates (i.e., the particle shrinkage ratio can be decreased by up to ∼90%, and the particle surface loss ratio can be decreased by up to ∼50%). The discrepancy becomes notably more pronounced at elevated temperatures, where the sintering of Al nanoparticles in the aerosol phase is very fast. The effect of CF addition is to trap burning particles close to the burning surface for a longer time, thereby enhancing heat feedback. This simulation work provides an atomistic-level explanation for our previous experimental works ( ACS Appl. Mater. Interfaces 2021, 13, 30504–30511 and Chem. Eng. J. 2023, 460, 141653).