A model for multicomponent diffusion in oxide melts. (March 2021)

• Record Type: Journal Article
• Authors: Kwon, Sun Yong; Hill, Reghan J.; Jung, In-Ho
• Is Part Of: Calphad. Volume 72(2021)
• Publication Date: 2021-03
• Subjects: Single-ion activity -- Multicomponent diffusion -- Oxide melts -- Electrolytes -- Non-equilibrium thermodynamics -- Entropy production; Phase diagrams -- Data processing -- Periodicals; Thermochemistry -- Data processing -- Periodicals; Diagrammes de phases -- Informatique -- Périodiques; Thermochimie -- Informatique -- Périodiques; Thermodynamica; Electronic journals; 541.363
• DOI: 10.1016/j.calphad.2020.102246
• Languages: English
• ISSNs: 0364-5916

Abstract

Abstract: A general flux equation for multicomponent diffusion in oxide melts is presented. An explicit method was developed to calculate the gradients of single-ion activities from those of oxides with the constraints of local equilibrium and electroneutrality. This resolves ambiguity in quantifying the thermochemical driving force for ionic diffusion. A model equation for multicomponent ionic diffusion was derived within the framework of non-equilibrium thermodynamics by de Groot and Mazur. The proposed model takes empirically measurable quantities as input variables, so the diffusion calculations are consistent with thermochemical data, as furnished by the CALPHAD (CALculation of PHAse Diagrams) method, as well as ionic mobility measurements. Although the model is derived for oxides, it can be applied to diffusion in other concentrated liquid electrolytes, such as chloride and fluoride melts. Formulas for multicomponent ionic diffusion in various reference frames are presented with respect to mole fraction. Graphical abstract: Highlights: A framework was developed to assess single-ion activity gradients in ionic melts. The proposed ionic flux takes empirically measurable quantities as input variables. Formulas were derived for stationary coordinates and mean-velocity reference frames.