The mechanical and thermal responses of colliding oxide-coated aluminum nanoparticles
B Ma and F Zhao and XL Cheng and F Miao and JD Zhang, JOURNAL OF APPLIED PHYSICS, 121, 145108 (2017).
The aggregation and fracture of oxide-coated metal nanoparticles have a significant influence on their physical and chemical behaviors in synthesis, combustion, or detonation. How does the dynamic loading caused by the impact between nanoparticles affect them? Motivated by this issue, we carried out molecular dynamic simulations of two colliding aluminum nanoparticles to investigate their mechanical and thermal properties and response at impact velocities of 200 m/s, 600 m/s, 1000 m/s, and 2000 m/s. At the relatively low impact velocities (equal to or less than 1000 m/s), it was observed that the particles are mildly deformed and adhere to each other, but the shells do not undergo fracture under the dynamic loading. The metal core and oxide shell behave elastically at 200 m/s and elasto-plastically at 600 m/s. A concentration of dynamic volumetric stress appears but no concentration of shear stress and no formation of a hot spot. Due to the low intensity of the loading and the efficient propagation of the stress wave, the shells fail to fracture. At an impact velocity of 2000 m/s, the impact region of the shell undergoes ductile fracture, and the two particles undergo sintering and form a new particle re-coated with oxide, resulting from the concentration of dynamic shear stress and the formation of a hot spot. At all impact velocities in our simulations, the impact between the nanoparticles improves the aggregation but has a little effect on the fracture of the oxide shell. Published by AIP Publishing.
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