Phase Equilibria Diagrams Database

The most important representatives of tetravalent elements are titanium and zirconium because of their uses as advanced construction materials in different technologies. Systems of titanium and zirconium fluorides and chlorides with alkali metal fluorides and chlorides, respectively, can be found in the Phase Equilibria Diagrams Database (1993). A number of compounds with various stoichiometry are formed in these systems, depending on the size of the titanium and zirconium cation and the polarization ability of the alkali metal. Some of these compounds are very stable and melt congruently even at relatively high temperatures. On the other hand, some compounds melt incongruently and their existence is limited to a certain temperature range. 

Phase Equilibria Diagram Database (1993) NIST, Standard Reference Database 31, Version 2.1 for Windows 95, American Ceramic Society. 

It is known that in five of the six principal types of binary fluid phase equilibrium diagrams, data other than VLE may also be available for a particular binary (van Konynenburg and Scott, 1980). Thus, the entire database may also contain VL2E, VL E, VL]L2E, and L,L2E data. In this section, a systematic approach to utilize the entire phase equilibrium database is presented. The material is based on the work of Englezos et al. (1990b 1998)... 

This is a rather useful computer program that allows the user to make several types of calculations, including reaction enthalpies, heat balances, equilibrium compositions, and phase stability diagrams. The noncritically evaluated database contains more than 11,000 compounds. Updated versions are now available. 

The solution of problems in phase equilibrium is facilitated enormously if the phase diagram is known. Several systems have been studied experimentally and the results have been collected in extensive databases. However, given the inexhaustible variety of components, compositions, temperatures, and pressures, the chemical engineer will invariably be faced with components, or conditions, for which such data are not available. A main goal in much of the rest of this book is the development of methods to predict phase behavior where data are not available. 

The identification of the superconducting phase YBagCug-O7 g provides an example in which knowledge of thermodynamics, i.e. the Gibbs phase rule and the theory of equilibrium phase diagrams coupled with X-ray diffraction techniques led to success. Further, the use of databases that can now be easily accessed and searched on-line provided leads to a preliminary structure determination. The procedures outlined here are among the basic approaches used in solid state chemistry research, but by no means are they the only ones. Clearly the results from other analytical techniques such as electron microscopy and diffraction, thermal... 

The FACTSage thermochemical database was used to identify the thermodynamically stable phases that could exist in a system comprised of a pure metal, oxygen, HC1 and Cl2 at 500°C (Suppiah, 2008). The predominant Fe, Ni, Cu and Cr phases in an 02/HCl/Cl2 environment were determined. The equilibrium reaction boundary was plotted as a function of the partial pressures of 02 and HC1, for a constant Cl2 partial pressure. The resulting predominance diagrams were plotted over an 02 and HC1 partial pressure range of 10-20 to 1 atm for Cl2 partial pressures between 10-6 and 1 atm. The predominant Ni and Cr species are solids, suggesting that a corrosion resistant protective layer could be formed on the metal. 

One of the most powerful aspects of the HCToolkit is its extensibility in Perl. This allows rapid development of new applications for specific tasks. For example, an included extension quickly calculates and plots a pressure-temperature phase diagram at user-specified conditions (PT-PhaseDiagram.pl, found in the /apps subdirectory of the distribution tree). In fact, a scripting application that does some sort of equilibrium calculation needs only do four things create a database connection, use that connection to load a pre-defined fluid, initialize the flash object and do the flash calculation. These steps are shown in Figure 4. 

H. Okamoto (2000) Desk Handbook - Phase Diagrams for Binary Alloys, ASM International, ISBN 0 87170 682 2. Outokumpu (2010) HSC Chemistry for Windows. Chemical Reaction and Equilibrium Software with Extensive Thermochemical Database, Version 4.1, ISBN 952 9507 05 0. 

FactSage, with its modules to manipulate thermochemical databases and to calculate complex equilibrium states as well as multi-component phase diagrams, has been applied for the data compilation and assessment work described below as well as for the generation of the graphical results presented further below. 

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