The thermal decomposition of pure nitromethane (NM) and NM/nano-aluminum (Al) composites was simulated by reactive molecular dynamics with ReaxFF-lg corrected force field parameters. The initial decomposition pathway of NM molecules in pure NM is C-N bond rupture. However, NM is decomposed early by the initial pathway of N-O bond rupture when it mixes with nano-Al because of the strong attraction of Al to O. The decomposition process of NM/nano-Al can be divided into three stages: adsorption, slow decomposition, and rapid decomposition. The addition of nano-Al particles decreases the energy barrier in decomposition, increases the released energy, and reduces the decomposition temperature of NM. Adding 3% Al to the explosive can make the detonation pressure 3.083% higher than that of pure system. Compared with pure NM, the energy barrier of 16% Al composite is 25.63 kcal/mol lower and the energy released is 22.99 kcal/mol more. There is an optimal amount of Al contents being added to the NM composite by which the largest total numbers of gaseous products (N2, H2O, and CO2) are released. The effect of Al additives on CO2 production is the most obvious. The maximum detonation pressure can be achieved by adding an appropriate amount of nano-Al, which is similar to the experimental results. Graphical abstract.
Keywords: Decomposition pathway; Detonation pressure; Energy release; Nano-Al particles; ReaxFF-lg.