Details

Autor(en) / Beteiligte

• RAWLINGS, DAVID ALAN

Titel

THE ANALYSIS OF ION TRANSPORT IN GLASS-IONOMER SETTING REACTIONS

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

1987

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• A mathematical model of binary ionic interdiffusion and chemical reaction in and around a glass particle immersed in a solution of a weak polyacid has been constructed. The release from the glass of multi-valent cations which react with the polymer is described. The ionic groups in both the glass and the solution are considered to be partially dissociated and their concentrations obey respective equilibrium conditions. Two of the ions represented are exchanged between the two regions of the model whereupon they undergo irreversible reactions with the fixed ionic groups according to simple rate equations. A finite difference method for solution of the differential equations has been derived and its stability properties and truncation errors have been analysed. Results are presented which demonstrate the effect of partial ionic association on the kinetics of exchange and reaction. Application of the model to other cases of ionic diffusion/reaction is illustrated. A second model has been derived which is capable of describing systems with any number of diffusing species and the reactions which can occur between them. Although this model is physically homogeneous, and thus not directly applicable to the solid/liquid mixtures of the title, it does reveal relevant features which are not apparent in the simpler model. In particular, in the first model, a neutral shell can be formed which is impermeable to the mobile ions due to electrostatic repulsion. The second model illustrates how the presence of an additional mobile ion of opposite charge allows transfer to continue. The formation of an associated group which is more mobile than its constituents is illustrated. This has a significant effect on the system kinetics. The finite difference methods developed have been found to perform well with relatively coarse meshes.