CALPHAD Modeling of Phase Diagram Boundaries for Binary 2-Amino-2-Methyl-1,3-Propanediol [AMPL] and Tris(hydroxymethyl) Aminomethane [TRIS] system

The phase diagram assessment of binary AMPL-TRIS system was calculated using the CALPHAD approach. Thermo-Calc, TCC software was used to fit the experimental phase diagram data by simultaneous optimization of thermodynamic properties of pure components and phase equilibria data available in the literature, and also calculated in the present work. The measured interaction parameters for low temperature alpha and beta solid solution phases are relatively small and are assumed to be ideal. Preliminary calculation of AMPL-TRIS phase diagram showed complete solid solubility of the high temperature gamma and gamma-prime phases, as reported by Barrio et al. (1994). In the next iteration, we calculated AMPL-TRIS phase diagram using heat capacity data and found that it was in good agreement with the current experimental phase diagram developed by V. Kamisetty (2010). In final calculations, the Parrot module of Thermo-Calc program was used to obtain an optimized phase diagram. The calculated phase corroborates well with V. Kamisetty data. Two eutectoids, one at ~21 mol.% TRIS at 85oC, the other at ~60 mol. % TRIS at 104oC, and one peritectic at 55 mol.% TRIS at 127oC were calculated. The maximum solubility of TRIS in AMPL is 10 mol.%, and that of AMPL in TRIS is 18 mol.% at 85oC. An important feature of this phase diagram is the presence of gamma and gamma-prime phases above 110oC. Details of the methodology and calculations are shown in this thesis.