Thermo-Mechanical Behavior of Nickel-Coated Nano-Aluminum Particles

Abstract

Thermo-mechanical behavior of nickel coated nano-aluminum particles, in the size range of 4-16 nm, is studied using molecular dynamics simulations. The analysis is carried out in isothermal-isobaric and isochoric-isoenergetic ensembles using an embedded atom method. Emphasis is laid on analyzing the melting of Al core, diffusion of Al and Ni atoms, and intermetallic reactions for different core sizes and shell thicknesses. The melting point of the Al core is found to exceed the heterogeneous melting point of pure nAl particle and approach the homogenous melting point of Al, irrespective of the shell thickness. The diffusion of Al atoms, after melting, is accompanied by self-sustaining inter-metallic reactions between Al and Ni atoms. The advent of these reactions is, to some extent, delayed for a thicker shell and expedited for a larger core. The amount of heat release due to the reactions increases as the Al or Ni atomic fraction increases to 0.5. Adiabatic reaction temperatures close to 2300 K are predicted for near-equiatomic particles with a 1 nm thick Ni shell. The simulation results indicate the possibility of ignition of these particles in an inert environment and also help in explaining their reduced ignition temperatures.