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Experience teaches us, that under given external conditions a material is in a certain state. This state is defined by certain properties. At 200 K the compound H2O is solid, at 300 K liquid and at 400 K gaseous. Properties, which are characteristic for a state of a material, are called intensive properties. Among them is the molar volume. As one can see from Fig. 1.1, the molar volume of water is...
In a multi-component system at the solid-liquid equilibrium the compositions of the two coexisting phases are only equal in the case of a congruently melting compound, at the melting point maximum or minimum of a solution, and in the limiting case, of the melting point of a pure component. In general, a difference in composition exists between liquid and solid. This composition difference changes...
Organic materials and polymers represent important materials in our society; people studying and describing them also use thermodynamic means. The same thermodynamic conditions apply to them as to inorganic materials [1]. There are obviously structural differences between inorganic and organic materials. The building blocks of an inorganic phase diagram are molecules made up of a few (less than 10)...
As already presented in Sect. 1.2, some of the atoms or molecules tied to a solid or liquid, can, at a fixed temperature, leave the condensed phase. In a closed system a certain vapor pressure p is established, which depends, according to Eq. (1.1b), on the temperature. Equation (1.1b) is only valid when the enthalpy of vaporization dHV is independent of the temperature. This is not always true.
Experience has shown that, during cooling of a liquid, crystallization does not start immediately when the solidification temperature Tg is reached. The new phase is formed only after a more or less severe undercooling ΔT below the equilibrium temperature. This phenomenon is especially noticeable with transformation or precipitation reactions in solids. It is based on the fact, that in a situation,...
The combination of different substances into multi-component systems yields a large number of different phase diagrams The complex variety of phase diagrams is, however, conditioned only by the interaction of a few factors. Experience shows, that certain types of phase diagrams can be found in very different groups of substances. Simple eutectic systems can, for example, be found in the combination...
On melting a substance heat is absorbed in order to transform the crystal into the melt, in which the interatomic interaction is weaker. In addition, the degree of order is lower than in the solid body. The melting process is therefore connected with an absorption of heat (heat of melting or enthalpy of fusion) as well as with a volume change. This implies that the melting equilibria are determined...
The composition appears as a state variable in multi-component systems. For the description of atomic situations, its definition as atomic fraction or mol fraction x is especially useful.
The situation that, during nucleation of a new phase, the sum of the Gibbs energy terms, ΔG, contains terms with different signs, creates the possibility of the formation of metastable phases. This possibility will be explained based on Fig. 8.1.
This graduate-level textbook provides an introduction to the practical application of phase diagrams. It is intended for students and researchers in chemistry, metallurgy, mineralogy, and materials science as well as in engineering and physics. Heterogeneous equilibria are described by a minimum of theory illustrated by practical examples and realistic case discussions from the different fields of...
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