A thermodynamics model for morphology prediction of aluminum nano crystals fabricated by the inert gas condensation method

Abstract

The purpose of this study is to provide scientific guidance for the morphological control of nanoparticle synthesis using the gas phase method. A universal thermodynamics model is developed to predict the morphology of nanoparticles fabricated using the inert gas condensation method. By using this model, the morphologies of aluminum nanocrystals are predicted under various preparation conditions. There are two types of energy that jointly determine the formation of nanoparticle morphology-Gibbs free energy for nanoparticles and energy variation during the process. The results show that energy variation dominates morphology formation when the cooling rate is less than 2 × 10 K s in the aluminum nanocrystal production process. At the beginning of the nanoparticle growth, the most stable morphology is predicted to be spherical, but the energetically preferred morphology becomes cubic as the particle grows. The turning point in the particle size at which spherical morphology is no longer the most stable morphology is exhibited as a function of pressure in a condensation chamber for different cooling rates. In this paper, we focus on the need for morphology prediction based on preparation conditions. It is concluded that nanoparticles with various morphologies could be obtained by adjusting the cooling rate and pressure in the condensation chamber.

Numerical Method for Calculating Nanocrystals’ Edge Energies from Experimentally Observed Shape Evolution

“…Researchers have shown that the omission is valid for particles with diameters exceeding approximately 10 nm because the edges play a minor role in the particles’ equilibrium shape . For smaller nanoparticles it is ubiquitously believed that edge energies are a significant contributor to the total energies and should be considered in thermodynamic morphology models. − …”