浙江大学_材料热力学与动力学课件_1
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Chapter 1 : Thermodynamics and Phase Diagrams
1-13
1.1 Equilibrium in a Closed System
Phase : a portion of the system whose properties and composition are homogeneous, and is physically distinct from each other.
Chapter 1 : Thermodynamics and Phase Diagrams
1-14
How is system stability measured ? by its Gibbs free energy (at const. T and P)
G = H - TS
(1.1)
H : a measure of the heat content of the system ( H = U + PV ) S : a measure of the randomness of the system low T : TS small, solids are most stable (strongest atomic binding, low H) high T : TS dominates, liquids or gases are stable (atoms more free, high S)
1-6
At constant macroscopic velocities and constant position coordinates, the followings apply to
internal changes of state:
DU = W
adiabatic process
DU = 0
Open System can exchange mass, heat and work with its surroundings Closed System no mass exchange, heat and work exchange possible
Isolated System
Every thermodynamic system possesses an extensive property called entropy S. The change in entropy of a system is determinated by bring the system from an arbitrary initial state to a defined final state, whereby the system passes through a series of equilibrium states. At each step the quantity of heat dQ is added to the system. Division of dQ by the temperature T, and summation of the quotients dQ/T over all steps, yields the change in entropy of the system for the change of state.
1-17
Thermodynamic Functions
W = E2 - E1 = DE W > 0, work is done on the system W < 0, work is done by the system
isolated system closed system
W = 0, E = const.
DE = Q + W
Q > 0, system receives heat Q < 0, system loses heat
no mass, no heat, no work exchange
Chapter 1 : Thermodynamics and Phase Diagrams
1-3
1.0.2 The First Law of Thermodynamics
A. Energy, Heat and Work
The energy of an isolated system is constant
reversible process :
irreversible process : adiabatic process : irr. adiabatic process : rev. adiabatic process :
Chapter 1 : Thermodynamics and Phase Diagrams
The Second Law of Thermodynamics
The entropy of a closed system can not decrease.
Clausius: Heat can not flow automatically from cold side to hot side. Planck: Such a process is impossible if its only result were to exchange heat to work.
perpetual machines
type I
type II
1-12
Chapter 1 : Thermodynamics and Phase Diagrams
Heat can not flow automatically from cold side to hot side !!! Mr. Tompkins in Paperback G. Gamow Cambridge University Press, 1965
for an infinitesimal change of state in a closed system dE = dQ + dW
Chapter 1 : Thermodynamics and Phase Diagrams
1-5
B. Internal Energy
The total energy E of a system is made up of its kinetic energy E kinetic , its potential energy E potential and its internal energy U
dH = dU + VdP
DH = Q
(at constant P)
U CV T V
ቤተ መጻሕፍቲ ባይዱ
U CP T P
1-8
Chapter 1 : Thermodynamics and Phase Diagrams
1.0.3 The Second Law of Thermodynamics Entropy
A given system can exist as a mixture of one or more phases, which can change into a new phase or mixture of phases.
Why ?
the initial state of the system is unstable relative to the final state
Chapter 1 : Thermodynamics and Phase Diagrams
1-15
Stable, Metastable and Unstable
C
G dG = 0
dG = 0
B A
dG = 0
B A
B C
C
A
Stable: graphite, single crystal silicon
DU = Q + W
dU = dQ - PdV
isolated system
closed system
Chapter 1 : Thermodynamics and Phase Diagrams
1-7
C. Enthalpy and Heat Capacity H = U + PV
(definition)
D S
T 0
T 1
dQ
T
dS
1-9
Chapter 1 : Thermodynamics and Phase Diagrams
Bolztmann’s Equation
S = k lnW k = 1.38065810-23 J/K : Bolztmann’ Constant W : number of possible arrangements of atoms
Possibility and Realizability : Thermodynamics and Kinetics
G
Energy Hump
G1
G2
B C A
DG = G2 – G1 < 0 : only possible for the transformation from B to A
Amorphous Alloy (short-lived), Diamond (long-lived) Temperature : kinetic key (vibration frequency and amplitude) Chapter 1 : Thermodynamics and Phase Diagrams
DSinner : from inner processes DSexner : due to heat exchange
Q
DSexter
DSinner
DS i = 0, DS = DS e DS i > 0, DS > DS e DS e = 0, DS = DS i DS > 0 DS = 0
1-11
Chapter 1.
Thermodynamics and Phase Diagrams
Prof. Dr. X.B. Zhao
Department of Materials Science and Engineering Zhejiang University
Chapter 1 : Thermodynamics and Phase Diagrams
The work done on a thermally isolated system is independent of the type of work and the route
Chapter 1 : Thermodynamics and Phase Diagrams
1-4
state 1 to 2 :
1-1
1.0.1 Thermodynamics Systems
Homogeneous System
with the same physical and chemical properties
Heterogeneous System
being made of several phases
1-2
Chapter 1 : Thermodynamics and Phase Diagrams
Metastable: diamond, amorphous Unstable: super-cooling liquid (nucleation)
an arbitrary state parameter
Chapter 1 : Thermodynamics and Phase Diagrams
1-16
E = E kinetic + E potential + U Law of Conservation of Energy for an isolated system E kinetic + E potential + U = const.
Chapter 1 : Thermodynamics and Phase Diagrams
Entropy is a state function. For a reversible cyclic process:
D S Q T 0 d
Chapter 1 : Thermodynamics and Phase Diagrams
1-10
2 parts of DS (inner and external)
1-13
1.1 Equilibrium in a Closed System
Phase : a portion of the system whose properties and composition are homogeneous, and is physically distinct from each other.
Chapter 1 : Thermodynamics and Phase Diagrams
1-14
How is system stability measured ? by its Gibbs free energy (at const. T and P)
G = H - TS
(1.1)
H : a measure of the heat content of the system ( H = U + PV ) S : a measure of the randomness of the system low T : TS small, solids are most stable (strongest atomic binding, low H) high T : TS dominates, liquids or gases are stable (atoms more free, high S)
1-6
At constant macroscopic velocities and constant position coordinates, the followings apply to
internal changes of state:
DU = W
adiabatic process
DU = 0
Open System can exchange mass, heat and work with its surroundings Closed System no mass exchange, heat and work exchange possible
Isolated System
Every thermodynamic system possesses an extensive property called entropy S. The change in entropy of a system is determinated by bring the system from an arbitrary initial state to a defined final state, whereby the system passes through a series of equilibrium states. At each step the quantity of heat dQ is added to the system. Division of dQ by the temperature T, and summation of the quotients dQ/T over all steps, yields the change in entropy of the system for the change of state.
1-17
Thermodynamic Functions
W = E2 - E1 = DE W > 0, work is done on the system W < 0, work is done by the system
isolated system closed system
W = 0, E = const.
DE = Q + W
Q > 0, system receives heat Q < 0, system loses heat
no mass, no heat, no work exchange
Chapter 1 : Thermodynamics and Phase Diagrams
1-3
1.0.2 The First Law of Thermodynamics
A. Energy, Heat and Work
The energy of an isolated system is constant
reversible process :
irreversible process : adiabatic process : irr. adiabatic process : rev. adiabatic process :
Chapter 1 : Thermodynamics and Phase Diagrams
The Second Law of Thermodynamics
The entropy of a closed system can not decrease.
Clausius: Heat can not flow automatically from cold side to hot side. Planck: Such a process is impossible if its only result were to exchange heat to work.
perpetual machines
type I
type II
1-12
Chapter 1 : Thermodynamics and Phase Diagrams
Heat can not flow automatically from cold side to hot side !!! Mr. Tompkins in Paperback G. Gamow Cambridge University Press, 1965
for an infinitesimal change of state in a closed system dE = dQ + dW
Chapter 1 : Thermodynamics and Phase Diagrams
1-5
B. Internal Energy
The total energy E of a system is made up of its kinetic energy E kinetic , its potential energy E potential and its internal energy U
dH = dU + VdP
DH = Q
(at constant P)
U CV T V
ቤተ መጻሕፍቲ ባይዱ
U CP T P
1-8
Chapter 1 : Thermodynamics and Phase Diagrams
1.0.3 The Second Law of Thermodynamics Entropy
A given system can exist as a mixture of one or more phases, which can change into a new phase or mixture of phases.
Why ?
the initial state of the system is unstable relative to the final state
Chapter 1 : Thermodynamics and Phase Diagrams
1-15
Stable, Metastable and Unstable
C
G dG = 0
dG = 0
B A
dG = 0
B A
B C
C
A
Stable: graphite, single crystal silicon
DU = Q + W
dU = dQ - PdV
isolated system
closed system
Chapter 1 : Thermodynamics and Phase Diagrams
1-7
C. Enthalpy and Heat Capacity H = U + PV
(definition)
D S
T 0
T 1
dQ
T
dS
1-9
Chapter 1 : Thermodynamics and Phase Diagrams
Bolztmann’s Equation
S = k lnW k = 1.38065810-23 J/K : Bolztmann’ Constant W : number of possible arrangements of atoms
Possibility and Realizability : Thermodynamics and Kinetics
G
Energy Hump
G1
G2
B C A
DG = G2 – G1 < 0 : only possible for the transformation from B to A
Amorphous Alloy (short-lived), Diamond (long-lived) Temperature : kinetic key (vibration frequency and amplitude) Chapter 1 : Thermodynamics and Phase Diagrams
DSinner : from inner processes DSexner : due to heat exchange
Q
DSexter
DSinner
DS i = 0, DS = DS e DS i > 0, DS > DS e DS e = 0, DS = DS i DS > 0 DS = 0
1-11
Chapter 1.
Thermodynamics and Phase Diagrams
Prof. Dr. X.B. Zhao
Department of Materials Science and Engineering Zhejiang University
Chapter 1 : Thermodynamics and Phase Diagrams
The work done on a thermally isolated system is independent of the type of work and the route
Chapter 1 : Thermodynamics and Phase Diagrams
1-4
state 1 to 2 :
1-1
1.0.1 Thermodynamics Systems
Homogeneous System
with the same physical and chemical properties
Heterogeneous System
being made of several phases
1-2
Chapter 1 : Thermodynamics and Phase Diagrams
Metastable: diamond, amorphous Unstable: super-cooling liquid (nucleation)
an arbitrary state parameter
Chapter 1 : Thermodynamics and Phase Diagrams
1-16
E = E kinetic + E potential + U Law of Conservation of Energy for an isolated system E kinetic + E potential + U = const.
Chapter 1 : Thermodynamics and Phase Diagrams
Entropy is a state function. For a reversible cyclic process:
D S Q T 0 d
Chapter 1 : Thermodynamics and Phase Diagrams
1-10
2 parts of DS (inner and external)