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Gibbs free energy

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Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420041
EISBN: 978-1-62708-310-2
... Abstract This chapter explains how the principles of chemical thermodynamics are used in the construction and interpretation of phase diagrams. After a brief review of the laws of thermodynamics, it describes the concept of Gibbs free energy and its application to transformations that occur in...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.t65940023
EISBN: 978-1-62708-302-7
... Abstract This chapter provides a thorough introduction to the electrochemical thermodynamics that govern electrode reactions associated with corrosion. It begins with a review of the thermodynamic criteria for the stability of chemical reactions based on Gibbs free energy and explains how...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.t65940001
EISBN: 978-1-62708-302-7
... occurs), it is necessary to calculate the Gibbs free-energy change and find that it is negative. To make this calculation requires quantitative information on the activity or effective concentration of iron ions (a Fe 2+ ) in the solution, the acidity, or pH, and the concentration of dissolved oxygen...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 October 2011
DOI: 10.31399/asm.tb.mnm2.t53060013
EISBN: 978-1-62708-261-7
... equilibrium phase diagrams, the role of enthalpy and Gibb’s free energy in chemical reactions, and a method for determining phase compositions along the solidus and liquidus lines. atomic diffusion body-centered cubic systems crystal defects equilibrium phase diagram face-centered cubic systems...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2009
DOI: 10.31399/asm.tb.bcp.t52230513
EISBN: 978-1-62708-298-3
... C. , 2004 . “ Workers at the Energy Department’s Gaseous Diffusion Plants in Kentucky and Ohio Have Been Exposed to Beryllium ,” cfreyssi-group.net • IARC , 1994 . Beryllium, Cadmium, Mercury and Exposures in the Glass Manufacturing Industry , IARC Monographs on the Evaluation of...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.tb.ssde.t52310281
EISBN: 978-1-62708-286-0
... through a representation of the Gibbs energies of the different crystalline phases relevant to that system and defined by the chemical composition of the system. Thermo-Calc minimizes the total Gibbs energy of the system with respect to various constraints such as temperature, pressure, and chemical...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420001
EISBN: 978-1-62708-310-2
..., it is necessary that each be internally in a homogeneous state. In general, this means that each phase must be in the lowest free energy state possible under the restrictions imposed by its environment. Thus, the chemical composition must be identical everywhere within the phase, the molecular and...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 June 2008
DOI: 10.31399/asm.tb.emea.t52240053
EISBN: 978-1-62708-251-8
... randomness of the system. Solving for F , the Helmholtz free energy, can be expressed as: (Eq 4.2) F = E − T S A related free energy is the Gibbs free energy, which is defined as: (Eq 4.3) G = H − T S where H is enthalpy. The enthalpy, H , at constant pressure is...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 June 2008
DOI: 10.31399/asm.tb.emea.t52240075
EISBN: 978-1-62708-251-8
... homogenization) to create more uniform structures prior to hot working or heat treating. The shapes of liquidus, solidus, and solvus curves in a phase diagram are determined by the Gibbs free energies of the relevant phases. In this instance, the Gibbs free energy must include not only the energy of...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420015
EISBN: 978-1-62708-310-2
... the sum of the free energy, F , and the bound energy ( TS ): (Eq 2.1) E = F + T S where E is the internal energy, F is the Hemholtz free energy, T is the absolute temperature in degrees Kelvin (K), and S is entropy, a measure of the randomness of the system. The Gibbs free...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 1999
DOI: 10.31399/asm.tb.cmp.t66770051
EISBN: 978-1-62708-337-9
... nitrogen are austenite formers. Fig. 3.1 Gibbs energy (Δ G plotted against the interaction energy (W x ) for alloying elements added to steel. In the standard range of carburizing steels, the carbides formed will have the Fe 3 C (cementite) structure, in which atoms of carbide-forming...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2015
DOI: 10.31399/asm.tb.spsp2.t54410551
EISBN: 978-1-62708-265-5
... This chapter describes surface modification processes that go beyond conventional heat treatments, including plasma nitriding, plasma carburizing, low-pressure carburizing, ion implantation, physical and chemical vapor deposition, salt bath coating, and transformation hardening via high-energy...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2016
DOI: 10.31399/asm.tb.ascaam.9781627082969
EISBN: 978-1-62708-296-9
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.tb.ssde.t52310011
EISBN: 978-1-62708-286-0
... addition of a variable resistor and a voltmeter, resulting in the arrangement shown in Fig. 1(b) . Thermodynamically, the Gibbs free energy of the cell is that of Reaction 1: (Eq 5) Δ G = Δ H − T Δ S    = Δ G 0 + R T ln ( a OH - ) 4 ( a...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2016
DOI: 10.31399/asm.tb.ascaam.t59190173
EISBN: 978-1-62708-296-9
... V volume ν R growth rate of solid phase (crystal), Δ x /Δ t V v volume fraction of phase ν T cooling rate, Δ T /Δ t θ wetting angle ξ crystallographic factor Δ C difference in concentration Δ G driving force of transformation, Gibbs free energy Δ G N...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.tb.ssde.t52310057
EISBN: 978-1-62708-286-0
... oxide species also need to be considered. The standard Gibbs free energy Δ G 0 is often presented in Richardson-Jeffes (Gibbs free energy-temperature) diagrams such as the one shown in Fig. 1 ( Ref 4 ). Fig. 1 Standard Gibbs free energy of formation of some metal oxides as a function of...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 June 2008
DOI: 10.31399/asm.tb.emea.t52240063
EISBN: 978-1-62708-251-8
... above absolute zero, by far the most important case of diffusion occurs when there is a concentration gradient. In this case, the driving force for diffusion is to reduce the Gibbs free energy of the system. For example, if two blocks of the same A-B alloy composition are welded together ( Fig. 5.1...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420339
EISBN: 978-1-62708-310-2
... ) therefore occurs at a higher solute concentration. Fig. 16.9 (a) Gibbs free-energy composition diagram and (b) locus of solvus curves of metastable and stable equilibrium phases in a precipitation sequence. (a) The points of common tangency show the relationship between compositions of the matrix...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.tb.ssde.t52310155
EISBN: 978-1-62708-286-0
...  ( solid ) + y C  = y CO  (gas) +Cr The equilibrium for this reaction is: (Eq 2) L n  ( K ) = − Δ G 4575 T where K is the equilibrium constant, and G is the Gibbs free energy. Working through the thermodynamics yields the relationship that summarizes the...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.tb.cub.9781627082501
EISBN: 978-1-62708-250-1