Wetting and evaporation of salt-water nanodroplets: a molecular dynamics investigation

Jun Zhang, Matthew K. Borg, Khellil Sefiane, Jason M. Reese

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Abstract

We employ molecular dynamics simulations to study the wetting and evaporation of salt-water nanodroplets on platinum surfaces. Our results show that the contact angle of the droplets increases with the salt concentration. To verify this, a second simulation system of a thin salt-water film on a platinum surface is used to calculate the various surface tensions. We find that both the solid-liquid and liquid-vapor surface tensions increase with salt concentration and as a result these cause an increase in the contact angle. However, the evaporation rate of salt-water droplets decreases as the salt concentration increases, due to the hydration of salt ions. When the water molecules have all evaporated from the droplet, two forms of salt crystals are deposited, clump and ringlike, depending on the solid-liquid interaction strength and the evaporation rate. To form salt crystals in a ring, it is crucial that there is a pinned stage in the evaporation process, during which salt ions can move from the center to the rim of the droplets. With a stronger solid-liquid interaction strength, a slower evaporation rate, and a higher salt concentration, a complete salt crystal ring can be deposited on the surface.

Original languageEnglish
Article number052403
Number of pages11
JournalPhysical Review E
Volume92
Issue number5
DOIs
Publication statusPublished - 20 Nov 2015

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Keywords

  • contact angle
  • drops
  • evaporation
  • liquids
  • molecular dynamics
  • molecules
  • platinum
  • surface tension
  • evaporation process
  • liquid-vapor surfaces
  • molecular dynamics simulations
  • platinum surface
  • salt concentration
  • simulation systems
  • solid-liquid interaction
  • water nanodroplets

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