Phase Diagrams and Thermodynamic Modeling of Solutions

Arthur D. Pelton

• Publisher: Elsevier
• Year: 2018
• Print ISBN:
  9780128014943
• eBook ISBN:
  9780128016695
• Topic: Physical Sciences
• Subtopic: Physical & Theoretical Chemistry

Phase Diagrams and Thermodynamic Modeling of Solutions provides readers with an understanding of thermodynamics and phase equilibria that is required to make full and efficient use of these tools. The book systematically discusses phase diagrams of all types, the thermodynamics behind them, their calculations from thermodynamic databases, and the structural models of solutions used in the development of these databases. Featuring examples from a wide range of systems including metals, salts, ceramics, refractories, and concentrated aqueous solutions, Phase Diagrams and Thermodynamic Modeling of Solutions is a vital resource for researchers and developers in materials science, metallurgy, combustion and energy, corrosion engineering, environmental engineering, geology, glass technology, nuclear engineering, and other fields of inorganic chemical and materials science and engineering. Additionally, experts involved in developing thermodynamic databases will find a comprehensive reference text of current solution models. - Presents a rigorous and complete development of thermodynamics for readers who already have a basic understanding of chemical thermodynamics - Provides an in-depth understanding of phase equilibria - Includes information that can be used as a text for graduate courses on thermodynamics and phase diagrams, or on solution modeling - Covers several types of phase diagrams (paraequilibrium, solidus projections, first-melting projections, Scheil diagrams, enthalpy diagrams), and more

Part I

Phase Diagrams and Thermodynamics

1

Introduction

Abstract

A phase diagram is a graphic representation of the values of the thermodynamic variables when equilibrium is established among the phases of a system. Materials scientists are most familiar with phase diagrams that involve temperature and composition as variables. However, many useful phase diagrams can be drawn that involve other variables such as pressure, chemical potentials, volume, and enthalpy. This chapter presents a few examples of the many different kinds of possible phase diagrams for systems with one, two, three, or more components.

Keywords

Phase diagrams; Thermodynamics; Thermodynamic variables

A phase diagram is a graphic representation of the values of the thermodynamic variables when equilibrium is established among the phases of a system. Materials scientists are most familiar with phase diagrams that involve temperature, T, and composition as variables. Examples are T-composition phase diagrams for binary systems such as Fig. 1.1 for the Fe-Mo system, isothermal phase diagram sections of ternary systems such as Fig. 1.2 for the Zn-Mg-Al system, and isoplethal (constant composition) sections of ternary and higher-order systems such as Figs. 1.3A and 1.4.

Fig. 1.1 Temperature-composition phase diagram at P = 1 bar of the Fe-Mo system (Pelton, 2014).

Fig. 1.2 Isothermal phase diagram section at 25°C and P = 1 bar of the Zn-Mg-Al system (Pelton, 2014).

Fig. 1.3 Isoplethal phase diagram section at X_Zn = 0.1 and P = 1 bar of the Zn-Mg-Al system. (A) Temperature versus composition; (B) enthalpy versus composition (Pelton, 2014).

Fig. 1.4 Phase diagram section of the Fe-Cr-V-C system at 850°C, 0.3 wt% C, and P = 1 bar (SGTE).

However, many useful phase diagrams can be drawn that involve variables other than T and composition. The diagram in Fig. 1.5 shows the phases present at equilibrium in the Fe-Ni-O₂ system at 1200°C as the equilibrium oxygen partial pressure (i.e., chemical potential) is varied. The x-axis of this diagram is the overall molar metal ratio in the system. The phase diagram in Fig. 1.6 shows the equilibrium phases present when an equimolar Fe-Cr alloy is equilibrated at 925°C with a gas phase of varying O₂ and S₂ partial pressures. For systems at high pressure, P-T phase diagrams such as the diagram for the one-component Al₂SiO₅ system in Fig. 1.7A show the fields of stability of the various allotropes. When the pressure in Fig. 1.7A is replaced by the volume of the system as y-axis, the “corresponding” V-T phase diagram of Fig. 1.7B results. The enthalpy of the system can also be a variable in a phase diagram. In the phase diagram in Fig. 1.3B, the y-axis of Fig. 1.3A h...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Acknowledgments
• Introduction
• Part I: Phase Diagrams and Thermodynamics
• Part II: Thermodynamic Modeling of Solutions
• Exercises
• Index