Thermodynamic Investigation of the Effect of Interface Curvature on Solid-Liquid Equilibrium and Its Application to Zinc-Air Battery Electrolyte at Low Temperature

• Author / Creator

  Liu, Fanghui

• Micro and nanoscale confinements and local curvatures, which are ubiquitous in natural and man-made materials and systems, cause significant impact on thermodynamic phase behavior. This effect has been extensively studied for single component solid's liquid phase transitions, but rarely for multicomponent systems. Using Gibbsian thermodynamics, we derived an expression to describe the thermodynamic solid'liquid equilibrium for multicomponent systems, where the equation takes thermal, mechanical and chemical equilibrium conditions into account. This derivation highlights the equivalence of general forms of the Gibbs'Thomson and Ostwald'Freundlich equations. We show the effect of the radius of curvature of the solid'liquid interface on the phase diagram, where the equation can be applied to the entire composition range. The equation can predict the effect of curvature on both the freezing and precipitating processes, thus a precise expression for the curvature-induced eutectic point shift is also derived. The water/glycerol system, which has complete mixing of the two components in the liquid phase but nearly pure solid phases during freezing and precipitating processes, is chosen to explore these equations. Here, we predict the curvature effect on the freezing and precipitating process of the entire phase diagram, and the eutectic point temperature and concentration shift with curvature. We also applied the equations to the freezing behavior of the aqueous electrolytes that are actively used in zinc'air batteries. The osmotic virial equation is an accurate, straightforward way to describe the nonideality of aqueous solution as a function of concentrations. Here, osmotic virial coefficients of various electrolytes which are commonly used are found by fitting literature data, and the nanoscale confinement effect on the freezing point of electrolyte systems is also investigated. The theoretical studies in this thesis, which used thermodynamic analysis to investigate the nanoscale confinement effect on multicomponent solid'liquid equilibrium systems, can find crucial applications in cryobiology, soil science, synthetic nanoporous materials and other various nanoscience fields.

• Subjects / Keywords

  • Phase diagram
  • Thermodynamics
  • Solid liquid equilibrium

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3QF8K08S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.