Ice Nucleation on a Graphite Surface in the Presence of Nanoparticles

AK Metya and JK Singh, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 19056-19066 (2018).

DOI: 10.1021/acs.jpcc.8b05989

In this work, we have carried out a systematic study of nucleation of a supercooled nanofluid droplet on a graphite substrate using molecular dynamics simulations. In particular, the effect of nanoparticle (NP) loading (phi(s) up to 12.0 vol %) in the supercooled liquid and the interaction strength between water and NP (epsilon(NP-W)) on the behavior of ice nucleation is investigated. At lower epsilon(NP-W), the nucleation rate is indifferent, while at higher epsilon(NP-W), the nucleation rate is found to reduce with the addition of nanoparticles. We found the maximum rate of ice nucleation is at phi(s) = 1.91% and epsilon(NP-W) = 0.40 kcal/mol, which is approximately 45 times more than that seen in the bulk water. We present in detail the effect of nanoparticle and nanoparticle-water interactions on the structure and composition of ice. The results demonstrate that the number of ice-like water molecules in the nanofluid droplet decreases with increasing phi(s) and epsilon(NP-W), which correlates well with the lowering of the rate of ice nucleation at higher vol % of particle and stronger water- nanoparticle interaction. Therefore, the hydrophilicity of the nanoparticles inhibits nucleation. We further investigate the effect of the shape of nanoparticles on ice nucleation. The results suggest that the rate of ice nucleation is independent of particle shape of size similar to 1.2 nm. Finally, we try to draw a quantitative comparison with the water activity based ice nucleation theory.

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