Impact of Nanoscopic Impurity Aggregates on Cavitation in Water

TL;DR

This study demonstrates that nanoscopic hydrophobic impurities significantly lower water's cavitation threshold, explaining discrepancies between theory and experiments, and emphasizing the role of impurities in metastability.

Contribution

We combined molecular dynamics and classical nucleation theory to show how nanoscopic oil droplets influence cavitation thresholds in water, revealing impurities' critical impact.

Findings

Pure water withstands up to -120 MPa of tension

Nanoscopic oil droplets reduce cavitation threshold to around -30 MPa

Impurities limit the realization of theoretical tensile strength

Abstract

The stability of water against cavitation under negative pressures is a phenomenon known for considerable discrepancies between theoretical predictions and experimental observations. Using a combination of molecular dynamics simulations and classical nucleation theory, we explore how nanoscopic hydrocarbon droplets influence cavitation in water. Our findings reveal that while a macroscopic volume of absolutely pure water withstands up to -120 MPa of tension, introducing a single nanoscopic oil droplet, merely a few nanometers in radius, brings this cavitation threshold to around -30 MPa, closely matching the values typically observed in highly controlled experiments. The unavoidable presence of nanoscopic hydrophobic impurities, even in highly purified water used in experiments, imposes a practical limit on achieving the theoretical tensile strength in realistic settings. More broadly, our study highlights the profound impact of nonpolar residues on nucleation phenomena and enhances our understanding of metastability in real-world systems.