material science & thermodynamics presentation.pdf
TRANSCRIPT
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
1/48
11
EMA 4521CEMA 4521C
Materials Science IMaterials Science I
Lecture 1Lecture 1
Arvind AgarwalArvind Agarwal
Department of Mechanical and Materials EngineeringDepartment of Mechanical and Materials Engineering
Florida International UniversityFlorida International University
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
2/48
22
UniverseUniverse
System SurroundingsSystem Surroundings
ClosedClosed OpenOpen No matter enter or leavesNo matter enter or leaves Matter is allow to flowMatter is allow to flow
but energy can go in or outbut energy can go in or out in or outin or out
Boundaries may expand/contractBoundaries may expand/contract
due to work done by or on the systemdue to work done by or on the system
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
3/48
33
Combination of closedCombination of closedand open systemand open system
Car engineCar engine
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
4/48
44
Heat and workHeat and work
Energy transformedEnergy transformed
Heat (Q)Heat (Q) Work (W)Work (W)Transform occur Transform canTransform occur Transform can
due todue toTT occur by all othersoccur by all others
forms of energyforms of energy
(elect, magnetic,(elect, magnetic,mechmech))
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
5/48
55
ConventionConvention
When heat goes into theWhen heat goes into thesystem from surroundingsystem from surrounding
Q > 0Q > 0 QQ
Heat (Q) is energy in transitHeat (Q) is energy in transit
due to temp. differencedue to temp. difference((T)T)..
Q is aQ is aflowflowquantity andquantity andnot stored by the system.not stored by the system.
System storesSystem storesthermal/heat energythermal/heat energyandandnot heat.not heat.
Heat Energy is referred asHeat Energy is referred asEnthalpy (H)Enthalpy (H)
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
6/48
66
Enthalpy (H)Enthalpy (H)
Heat (Q) is transfer across the boundary ofHeat (Q) is transfer across the boundary ofa system due to temperature differentiala system due to temperature differential
((T) between system and surroundings.T) between system and surroundings.
NoteNote: System: System does notdoes not contain heat (Q) butcontain heat (Q) butHeat Energy (H) . Heat is energy in transit.Heat Energy (H) . Heat is energy in transit.
Heat Energy is also referred as Enthalpy (H)Heat Energy is also referred as Enthalpy (H)
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
7/48
77
Internal EnergyInternal Energy
Total Energy can be divided as = KineticTotal Energy can be divided as = KineticEnergy + Potential Energy + InternalEnergy + Potential Energy + InternalEnergyEnergy
Thus, Total Energy= Internal Energy (U)Thus, Total Energy= Internal Energy (U) Internal Energy (U) is due toInternal Energy (U) is due toinherentinherent
qualities (motion of atoms and molecules inqualities (motion of atoms and molecules inthe matter) as well asthe matter) as well asenvironmentalenvironmental
variables (temp, pressure, elec. field,variables (temp, pressure, elec. field, magmag U= f (material properties, composition,U= f (material properties, composition,
pressure ,temperature)pressure ,temperature)
0
0
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
8/48
88
Basic Postulate ofBasic Postulate ofThermodynamicsThermodynamics
Entire concept is build on theEntire concept is build on theequilibriumequilibriumstatesstates
Postulate: Change in ThermodynamicPostulate: Change in Thermodynamic
PropertyProperty does notdoes notdepend on path thedepend on path thesystem took to get between two states.system took to get between two states.
It means that thermodynamic property isIt means that thermodynamic property is
dependent on INITIAL and FINAL stage onlydependent on INITIAL and FINAL stage only
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
9/48
99
State FunctionsState Functions
Thermodynamics properties DO NOT dependThermodynamics properties DO NOT dependon path, but depended on states.on path, but depended on states.
S,S,G,G,U all are state functions.U all are state functions.
Work done NOT a state functionWork done NOT a state function
Internal Energy State functionInternal Energy State function
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
10/48
1010
WorkWork
In contrast to U, WorkIn contrast to U, Workis not a state functionis not a state function
Work is pathWork is pathdependentdependent
(Path function(Path functionrepresented byrepresented by i.e.i.e.W)W)
Similarly, Q (heat) isSimilarly, Q (heat) is
also path dependentalso path dependentand written asand written as QQ
But loosely speakingBut loosely speakingwe keep on writingwe keep on writing QQ
== dQdQ andand W=W=dWdW
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
11/48
1111
First Law :First Law :Energy can not be created or destroyed.Energy can not be created or destroyed.
To derive practical benefits of this law, we are creating an accTo derive practical benefits of this law, we are creating an accountingounting
systemsystem needs defining various thermodynamic properties and rules.needs defining various thermodynamic properties and rules.
Total energy of systemTotal energy of systemplus surroundings is constantplus surroundings is constant
Conservation of EnergyConservation of Energy
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
12/48
1212
dQdQ
dWdW
dUdU== dQdQ dWdW dWdW ExpansionExpansion
Work doneWork done BYBY
the system =the system = PdVPdV Expansion:Expansion:
dVdV= V2= V2--V1V1
V2> V1V2> V1 dVdV> 0> 0 PdVPdV> 0> 0
dUdU== dQdQ PdVPdV
SameSame
So no difference just follow one??So no difference just follow one??
dQdQ dWdW
dUdU== dQdQ ++ dWdW dWdW ContractionContraction
Work doneWork done ONON thethesystem =system = PdVPdV
Contraction:Contraction:
dVdV= V2= V2--V1V1
V2< V1V2< V1 dVdV
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
13/48
1313
Enthalpy (H)Enthalpy (H)
Heat (Q) is transfer across the boundary ofHeat (Q) is transfer across the boundary ofa system due to temperature differentiala system due to temperature differential
((T) between system and surroundings.T) between system and surroundings.
NoteNote: System: System does notdoes not contain heat (Q)butcontain heat (Q)butHeat Energy (H) . Heat is energy in transit.Heat Energy (H) . Heat is energy in transit.
Heat Energy is also referred as Enthalpy (H)Heat Energy is also referred as Enthalpy (H)
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
14/48
1414
EnthalpyEnthalpy
Q=Q= dUdU ++ PdVPdV (from First Law)(from First Law)= d(U+PV) at constant pressure= d(U+PV) at constant pressure
Thus,Thus, Q=Q= dHdH at constant pressureat constant pressure H= U + PV is defined as enthalpyH= U + PV is defined as enthalpy
H0 Endothermic
QQ WW
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
15/48
1515
EnthalpyEnthalpy
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
16/48
1616
Intensive and ExtensiveIntensive and ExtensivePropertiesProperties
1.1. Extensive properties (Extensive properties (mass, volume,mass, volume,internal energyinternal energy) depend upon sample) depend upon sample
size.size.
2.2. Intensive properties (Intensive properties (temperature,temperature,
pressure, density, specific volumepressure, density, specific volume))
do not depend upon the sample size.do not depend upon the sample size.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
17/48
1717
Specific PropertiesSpecific Properties
Properties per unit mass (kg or mole) areProperties per unit mass (kg or mole) arespecific properties.specific properties.
E.g. U, V, G, Cp,E.g. U, V, G, Cp, CvCv
Per Mole properties are calledPer Mole properties are calledMolarMolarpropertiespropertiesQuestion 1: Are specific propertiesQuestion 1: Are specific propertiesintensiveintensiveoror
extensive?extensive?
Question 2: what is the specific volume of water?Question 2: what is the specific volume of water?Density = 1g/cc at 298 KDensity = 1g/cc at 298 K
Answer: 10 expAnswer: 10 exp3 m3/kg3 m3/kg
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
18/48
1818
Heat CapacityHeat Capacity
Energy regard to increase temperature of aEnergy regard to increase temperature of abody by 1K.body by 1K.
Specific Heat CapacitySpecific Heat Capacity::
Energy to raise the temperature of 1 gm ofEnergy to raise the temperature of 1 gm ofsubstance by 1 K.substance by 1 K.
Molar Heat CapacityMolar Heat Capacity::
Energy to raise the temperature of 1 mol ofEnergy to raise the temperature of 1 mol ofsubstance by 1 K.substance by 1 K.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
19/48
1919
Heat CapacityHeat Capacity
There are two definitions for vaporsThere are two definitions for vaporsand gases:and gases:
CpCp = Specific heat capacity at= Specific heat capacity at
constant pressure, i.e.constant pressure, i.e.
CvCv = Specific heat capacity at= Specific heat capacity at
constant volume, i.e.constant volume, i.e.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
20/48
2020
Most of the metallurgical proceduresMost of the metallurgical proceduresare at constant pressure rather thanare at constant pressure rather than
constant volumeconstant volume
At constant pressureAt constant pressure Q =Q = dHdH
T2T2 T2T2
dHdH == CpCp dTdT KirchoffKirchoffEqEq..T1T1 T1T1
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
21/48
2121
T2T2
H2H2 H1 =H1 = CpCp dTdTT1T1
T2T2
HH22(T)= H(T)= H1100 ++ CpCp dTdT
T1T1
EnthalpyEnthalpy at absolute zero cant be defined. But we doat absolute zero cant be defined. But we doneed a reference point. So, we choseneed a reference point. So, we chose
HH1100 : Reference State (298 K, 1: Reference State (298 K, 1 atmatm) occurs when) occurs whenelements exist in equilibrium conditionelements exist in equilibrium condition
E.g. Diatomic O2, pure Ag, pure Al, pure CuE.g. Diatomic O2, pure Ag, pure Al, pure Cu
HformationHformation < 0 ;< 0 ;HformationHformation > 0> 0
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
22/48
2222
For a reaction:For a reaction:
A + B C + DA + B C + D
T2T2
HH22(T)= H(T)= H1100 ++ [[CpCp productproduct++CpCp reactreact ]] dtdt
T1T1
By HessBy Hesss Laws Law
Enthalpy of formation when 1 mol ofEnthalpy of formation when 1 mol ofcompound ( product) is formedcompound ( product) is formed
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
23/48
2323
HessHesss Laws Law
If a reaction isIf a reaction iscarried out in acarried out in a
several steps,several steps,H ofH of
the reaction will bethe reaction will beequal to sum of theequal to sum of the
enthalpy changesenthalpy changes
for the individualfor the individual
step.step.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
24/48
2424
Latent HeatLatent Heat
Heat needed to change the state ofHeat needed to change the state ofmattermatter
S L VS L V
LLfusionfusion: quantity of heat energy released: quantity of heat energy releasedwhen 1 unit weight of a substancewhen 1 unit weight of a substance
solidifies without change thesolidifies without change thetemperaturetemperature
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
25/48
11
EMA 4521 CEMA 4521 C
Materials Science IMaterials Science I
Arvind AgarwalArvind Agarwal
Department of Mechanical and Materials EngineeringDepartment of Mechanical and Materials Engineering
Florida International UniversityFlorida International University
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
26/48
22
First LawFirst Law
dUdU == dQdQ ++ dWdWdUdU == dQdQ PdVPdV dQdQ
dQdQ == dUdU ++ PdVPdV
dQdQ
= d(U + PV) If P is constant= d(U + PV) If P is constant
dQdQ == dHdH H= U + PVH= U + PV dWdW
Heat Energy = Enthalpy at constant pressureHeat Energy = Enthalpy at constant pressure
H< 0 Exothermic (E.g.H< 0 Exothermic (E.g. ThermiteThermite reaction)reaction)H> 0 EndothermicH> 0 Endothermic
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
27/48
33
We defined heat capacityWe defined heat capacity
Cp = (Cp = (Q/Q/T)p = (T)p = (H/H/T)T) CvCv = (= (Q/Q/T)v = (T)v = (U/U/T)T)
T2 T2T2 T2
dHdH == CpdTCpdTT1 T1T1 T1
Cp = f(t)Cp = f(t)
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
28/48
44
HessHesss Laws Law
HessHesss Law: If a reaction is carried out in a series ofs Law: If a reaction is carried out in a series ofsteps,steps,H for the total reaction will be equal to theH for the total reaction will be equal to thesum ofsum ofHHii for each step.for each step.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
29/48
55
NewNew
Heat of ReactionHeat of Reaction
Heat of reaction: is the heat involved or absorbedHeat of reaction: is the heat involved or absorbedwhen reactants react completely to form products.when reactants react completely to form products.
(Unit:(Unit: -- per mole of any reactant or product)per mole of any reactant or product)
A + B C + DA + B C + D
Heat of =Heat of = Heat productHeat product -- Heat of reactantsHeat of reactants
reactionreaction
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
30/48
66
Example 1Example 1
CHCH44 + 2O+ 2O22 COCO22 + 2H+ 2H22O (g)O (g)
HH00reaction = 2reaction = 2HH00HH22O +O +HH00COCO22
-- 22HH00OO22 --HH00CHCH44
00
HH00
HH22O =O = --241.8 KJ241.8 KJHH00COCO22 == --393.5 KJ393.5 KJ
HH00CHCH44 == --74.8 KJ74.8 KJ
HH00reaction =reaction = --802 KJ at 298 K802 KJ at 298 K
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
31/48
77
Heat of FormationHeat of Formation
The heat of formation of a compoundThe heat of formation of a compound(per mole) is the heat evolved or(per mole) is the heat evolved or
absorbed (i.e. change in enthalpy)absorbed (i.e. change in enthalpy)
when 1 mole of compound forms fromwhen 1 mole of compound forms fromits constituents elements or substancesits constituents elements or substances
e.g. Ni(s) +e.g. Ni(s) + O2(g) =O2(g) = NiONiO (s)(s)
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
32/48
88
Heat of formation = f(temp, pressure,Heat of formation = f(temp, pressure,chemical state of reactants and products)chemical state of reactants and products)
Hence, we define heat of formation atHence, we define heat of formation at
standard state I.e. 298 K and 1standard state I.e. 298 K and 1AtmAtm.. Heat of formation of a compound from itsHeat of formation of a compound from its
standard statestandard stateis called Standard Heat ofis called Standard Heat of
Formation. It is denoted byFormation. It is denoted byHH00
298.298.i.e.i.e.HH00298, M298, M for a metal Mfor a metal M
Heat of FormationHeat of Formation
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
33/48
99
ConventionConvention
< M > solid< M > solid { M } liquid{ M } liquid
( M ) gas( M ) gas
Or Ms, MOr Ms, ML,L, MMG.G.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
34/48
1010
Concept of ReferenceConcept of ReferenceStateState
H = HH = H22 HH11 U, or H can never be defined inU, or H can never be defined in
absolute terms. There is no absoluteabsolute terms. There is no absolute
zero of energy.zero of energy.
There has to be some reference.There has to be some reference.
We define reference or standard stateWe define reference or standard state(25 degrees C or 298K and 1(25 degrees C or 298K and 1 atmatm))
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
35/48
1111
Major AssumptionMajor Assumption
Enthalpy (Enthalpy (HH00298298 )of O2 at reference)of O2 at reference
state = 0state = 0
Enthalpy (Enthalpy (HH00298298 )of pure substances)of pure substances
at reference state = 0at reference state = 0
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
36/48
1212
If pure elements/substances areIf pure elements/substances are
assumed to have zero enthalpy atassumed to have zero enthalpy atreference state their compound mustreference state their compound must
have some other values.have some other values.
ExampleExample
C + OC + O22 COCO22 (at 298 K)(at 298 K)
H react =H react = nnppproductsproducts nnrrreactionreaction==HcoHco22 --HcHc --HoHo22
0 00 0== --393.5 KJ/mol reference393.5 KJ/mol reference
statestate
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
37/48
1313
To findTo find
H at temperature other thanH at temperature other than
298 K298 K
((HH00
//T) =T) =CCppT1T1
HH00TT22 --HH
00TT11 == CpdTCpdT
T2T2
T1T1
HH00
TT22 ==HH00TT11 ++ CpCpprodprodCpCpreactreactT2T2
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
38/48
1414
Example 3Example 3
Page 10, Example 1.C,Page 10, Example 1.C, DubeDube UpadhyayaUpadhyaya BookBook
About + (O2) =
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
39/48
1515
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
40/48
1616
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
41/48
1717
Entropy and the SecondEntropy and the Second
Law of ThermodynamicsLaw of Thermodynamics
Second Law of thermodynamics defines a termSecond Law of thermodynamics defines a termentropyentropywhich tells aboutwhich tells aboutspontaneityspontaneityof theof thereaction or thereaction or thedirectiondirectionof the reaction.of the reaction.
The world is inherently active.The world is inherently active.
Whenever an energy distribution is out of equilibriumWhenever an energy distribution is out of equilibrium(e.g. temp. difference) a potential or thermodynamic(e.g. temp. difference) a potential or thermodynamic
"force"forceexists that the world acts spontaneously toexists that the world acts spontaneously todissipate or minimize.dissipate or minimize. (This minimization results in(This minimization results inmaximization of entropy)maximization of entropy)
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
42/48
1818
Reversible ProcessReversible Process
Reversible Process: is that whichReversible Process: is that whichhaven taken place could be reversedhaven taken place could be reversedand in doing so leaves no change isand in doing so leaves no change is
systemsystemororsurroundingsurrounding. (. (This mayThis may
happen if there is no friction, no unrestrained expansion andhappen if there is no friction, no unrestrained expansion andheat transfer only due to infinitesimal temperature difference)heat transfer only due to infinitesimal temperature difference)
For a reversible processFor a reversible processSSsystemsystem ++SSsurroundingsurrounding = 0= 0
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
43/48
1919
Irreversible ProcessIrreversible Process
Most of theMost of thenaturalnaturalprocesses areprocesses areirreversibleirreversible..
For an irreversible (I.e. spontaneousFor an irreversible (I.e. spontaneous
process)process)SSsystemsystem ++SSsurroundingsurrounding > 0> 0
Entropy is not conserved in naturalEntropy is not conserved in naturalprocesses.processes.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
44/48
2020
Entropy and the SecondEntropy and the Second
Law of ThermodynamicsLaw of Thermodynamics
The balance equation of the secondThe balance equation of the secondlaw, expressed as S > 0, says that inlaw, expressed as S > 0, says that in
allall naturalnaturalprocesses the entropy ofprocesses the entropy of
the world always increases.the world always increases.
Entropy is a measure of disorder.Entropy is a measure of disorder.
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
45/48
2121
Entropy: MathematicalEntropy: Mathematical
ConceptConcept
Entropy like energy is NOT conserved (Entropy like energy is NOT conserved (To prove:To prove:
Give as HW problemGive as HW problem))
dSdS== QrevQrev/T =/T = dHdH/T =/T = nCpdTnCpdT/ T/ T
Q =Q = dHdH (at const. Pressure)(at const. Pressure)
SS22 TT22 dsds == CpCp dTdT/T/T
SS11 TT11
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
46/48
2222
EntropyEntropy
State Function (Proof beyond thisState Function (Proof beyond thiscourse)course)
Extensive Property (i.e. depends onExtensive Property (i.e. depends on
mass or # of moles).mass or # of moles). Units: Cal/deg/mole orUnits: Cal/deg/mole or
Joules/deg/moleJoules/deg/mole
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
47/48
2323
Change in Enthalpy andChange in Enthalpy and
Entropy During MeltingEntropy During Melting
-
7/27/2019 Material Science & Thermodynamics Presentation.pdf
48/48
2424
Gibbs Free EnergyGibbs Free Energy
TheThe Gibbs Free EnergyGibbs Free Energyis a thermodynamicis a thermodynamicquantity which can be used to determine ifquantity which can be used to determine ifa reaction isa reaction is spontaneousspontaneous or not.or not.
The definition of the Gibbs free energy isThe definition of the Gibbs free energy is dGdG== dHdH TdSTdS. The sign of. The sign ofdGdG determines if adetermines if areaction is spontaneous or not.reaction is spontaneous or not.
dGdG < 0: the reaction is spontaneous< 0: the reaction is spontaneous
dGdG > 0: the reaction is not spontaneous> 0: the reaction is not spontaneous
dGdG = 0: the reaction is at= 0: the reaction is at equilibriumequilibrium