材料热力学-第五章02

Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
课程安排
1、相图热力学
2、相变热力学
3、化学反应热力学
Equilibrium and Minimum Internal Energy
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Finding Minimum Enthalpy Equilibrium and Thermodynamic
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
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Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
In an isolated unary two phase system if entropy is a maximum a) the temperature of the two phases will be equal so no heat will flow between the phases,
Finding Thermodynamic Equilibrium
Important!
Why? 1、Because it is difficult to find make systems ultra pure 2、Materials scientists engineer materials to have different properties by changing the material composition. For example 1、Steel, is an iron and carbon alloy with various other impurities added to change the alloy’s properties. 2、The silicon in integrated circuits is usually doped with impurities.
What does this mean physically?
Finding Thermodynamic Equilibrium
That particular type of atom or molecule adds a specific incremental amount of energy to the system
1、Temperature gradients are the potential for heat transfer When heat moves down a temperature gradient it lowers the temperature of the region it moves from and raises the temperature of the region it moves to 2 、 Pressure gradients are the driving force for bulk mass transport As the gas flows the pressure of the region left behind decreases and the pressure of the region the gas enters increases. 3 、 Chemical potential is the potential for differential mass transfer The chemical potential behaves exactly the same way. As a chemical species moves from a region of high chemical potential to a region of lower chemical potential the chemical potential from where the species came is lowered and the chemical potential of its destination is increased. Equilibrium is attained, and there is no driving force
How much? Depend on the local temperature, pressure and chemical composition. System like to decrease energy! In one portion of material Higher in chemical potential of a compotent means Higher energy, Decrease chemical potential! In solids, components are usually rearranged by diffusion so a chemical potential gradient of a component means there is a driving force for diffusion of that material to regions of lower chemical potential.
Finding Thermodynamic Equilibrium
b) the pressure of the two phases will be the same so neither phase will change its volume,
c) the chemical potential of the component is the same in each phase so there will be no net increase of component in either phase.
Equilibrium
Finding Thermodynamic Equilibrium
Equilibrium and Minimum F and G
Finding Thermodynamic Equilibrium
Finding Thermodynamic Equilibrium
Equilibrium in Multicomponent Heterogenous Systems A single component two phases more than one component more than two phases