Role of size effect and interface coarseness in energetic reactivity of Al/Cu nanoparticles

Using molecular dynamics simulation, we investigated the exothermic alloying procedure of Al/Cu nanoparticles with various sizes and interfacial contact areas. The results show that alloying reaction rates are determined by the diffusion barrier and contact area of initial configurations of Al/Cu nanoparticles. A higher interfacial diffusion barrier slows down the alloying rate of Al/Cu systems, while a larger interfacial contact area can accelerate the rate. During the alloying process, alloying reaction self-heating will occur slowly once an Al–Cu diffusion barrier is created at the interface, even though happening in the minimum size Al/Cu nanoparticle. Before the Al–Cu diffusion barrier layer appears at the interfaces, the melting of Al can make the alloying reaction more rapid. For the solid-state reaction of the Al/Cu interface, the larger interfacial contact area speeds up the alloying reaction of Al/Cu nanoparticles. The ignition temperature of Al/Cu nanoparticles is about 800 K, higher than our previous result (Tig = 700 K) of Al/Cu core–shell nanoparticles. It demonstrates that core–shell structure nanoparticles have a larger specific surface area and lower ignition temperature than the periodic nano-laminated structure.