STICT model for surface thermodynamics of liquid metal solutions

Abstract

A new model, called STICT for surface thermodynamics using ideal chemical theory, is developed for the surface tension of liquid metal alloys. It uses the Guggenheim approach to relate surface phase properties to those in the bulk. For strongly solvated metal mixtures, ideal chemical theory is used to characterize bulk properties. The STICT model fits experimental data well for the seven systems for which sufficient data exist. Moreover, calculations of bulk and surface true compositions give some guidance to the tailoring of the surface properties of alloys for various applications.

Application of the LCPT model to solid‐liquid equilibria for binary compound‐forming alloys

“…The latter two structural changes are not present in the phase transformation of a monatomic solid. An analysis of the true solution composition as a function of the bulk atomic composition for a specific alloy shows (Howell and Eckert, 1987): (1) the solutions are primarily composed of monomers; (2) the amount of each compound present peaks at its stoichiometric composition; and (3) the total amount of any one compound in solution, even at its stoichiometric composition, is inversely proportional to the size of the compound. This indicates that upon melting the liquid solution is more random, in that it comprises smaller species.…”

A comparison of the molecular interaction volume model with the subregular solution model in multicomponent liquid alloys

“…[8] and [10] into Eq. [7] and integrating it, one can obtain the equation of the coordination number of a liquid metal: [11] Suppose that the atoms of liquid metals are physical particles and the r 0i is the distance of the closest approach of the atoms, i , and the r mi is the average distance of the atoms at a constant temperature, d i , approximately, i.e., the former can be found from a textbook of crystal chemistry such as that of Evans, [17] and the latter can be calculated from [12] Thus, Eq.…”

“…Its characteristic is to contain a quantity of empirical parameters that need to be determined by fitting experimental data of mixtures, and to emphasize the accurate degree of actual estimation. Its representatives are regular solution model, subregular solution model, [7] and solution geometric model such as the Bonnier, Kohler, Toop, Muggianu, Colinet, and Chou-Wei [8] models, which are based on the regular solution theory; and quasi-chemical model, modified quasichemical model, [9] and local composition model such as Wilson and NRTL models that are based on the lattice theory; and the Tanaka-Gokcen-Morita model, [10] which is based on the free volume theory; and the Howell-Eckert model, [11] which is based on the associate solution theory; and the action concentration model, [12] which is based on the coexistence theory; and so on.…”

Chemical-physical model for the interfacial thermodynamics of liquid metal solutions

“…Most previous investigators (Taylor, 1956;Hoar and Melford, 1957;Kaufman, 1967;Laty et al, 1976;Bhatia and March, 1978;Okajima and Sakao, 1982; Angal and Roy, 1982; Howell and Eckert, 1987) have based their models of the surface thermodynamics of liquid alloys on the Gibbs or Guggenheim approaches (Defay and Prigogine, 1951;Guggenheim, 1952). These two approaches are 0888-5885/91/2630-1500$02.50/0 © 1991 American Chemical Society similar in that they view the system as consisting of a bulk phase in equilibrium with a surface phase.…”

“…Evidence supporting the formation of intermetallic compounds in liquid metal solutions includes the work of Wilson (1965), Steeb and Entress (1966), Steeb and Hezel (1966), Bhatia and Thornton (1970), Bhatia and Hargrove (1974), Bhatia et al (1974), Shimoji (1978), Jordan (1979), Predel (1979), Chieux and Ruppersberg (1980), Stoicos (1980), and Sommer (1982b). The surface properties are also affected by the formation of intermetallic compounds (Howell and Eckert, 1987). In order to model quantitatively the surface thermodynamics of these systems, it is important to account explicitly for the formation of intermetallic compounds in the liquid state.…”