文档介绍:Chapter two Metallurgical Thermodynamics Foundation
Several formulas
putation of and
~ graph and its application(Ellingham graph)
2017/11/11
. Several formulas
. Free energy ponent i in the system
1)the Gibbs free energy of ideal gas
in a sealed gas system which posed by ideal ponents,there ponents 1,2 ,……i,……,then the Gibbs free energy for ponent i is decided by
(2-1)
The equation of can be proved under the isothermal condition。
In which, is a nondimension pressure(note:in the realm of metallurgical physical chemistry, all the pressure inside the logarithmic symbol is nondimension pressure, like the pressure in the equilibrium constant )
(2-2)
- real pressure of ponent gas , ;
- standard pressure ,that is 。
it is worthy mentioning that, in the high temperature metallurgical process, gas is able to be regarded as ideal gas due to the low pressure.
2017/11/11
. Several formulas
2) the Gibbs free energy in liquid system
In the liquid system of ponents, there ponents 1,2 ,……i,……, then the Gibbs free energy for ponent i is decided by
In which , ---- activity of ponent,the principles to define standard state:
if i is in liquid iron,1% solution is the standard state,in which the concentration is percent of quality,[%i];
if i is in slag,the pure substance is the standard state , in which the concentration is percent of mol;
if i is the ferro element in liquid iron ,if the concentrations of ponents are little,the activity is 1;
2017/11/11
. Several formulas
3)the Gibbs free energy in solid system
In the solid system of ponents,there ponents 1,2 ,……i,……, then the Gibbs free energy for ponent i is decided by
In which, ---- activity of ponent,the principles to define standard state:
If the system is solid solution,then the activity of i in solid solution is pure substance, in which the concentration is percent of mol;
if the system is共晶体, then the activity of i in 共晶体中 is 1;
if the system is pure solid, then the