Phase Diagrams- Introduction - PowerPoint PPT Presentation

Loading...

PPT – Phase Diagrams- Introduction PowerPoint presentation | free to download - id: 6b6c8e-ZDRhY



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Phase Diagrams- Introduction

Description:

Title: Slide 1 Author: NR Last modified by: user Created Date: 9/20/2004 1:32:39 AM Document presentation format: On-screen Show Company: NIT Other titles – PowerPoint PPT presentation

Number of Views:5
Avg rating:3.0/5.0
Slides: 50
Provided by: NR
Learn more at: http://www.dss.nitc.ac.in
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Phase Diagrams- Introduction


1
Element Groups (Families) Element Groups (Families) Element Groups (Families)
Alkali Earth Alkaline Earth Transition Metals
Rare Earth Other Metals Metalloids
Non-Metals Halogens Noble Gases
2
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1 H He
1 -252.87 -268.6
2 Li Be B C N O F Ne
2 1347 2970 2550 4827 -195.8 -183 -188.14 -246.1
3 Na Mg Al Si P S Cl Ar
3 552.9 1107 2467 2355 280 444.6 -34.6 -186
4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
4 774 1484 2832 3287 3380 2672 1962 2750 2870 2732 2567 907 2403 2830 613 684.9 58.78 -153.4
5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
5 688 1384 3337 4377 4927 4612 4877 3900 3727 2927 2212 765 2000 2270 1750 989.8 184 -108.1
6 Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
6 678.4 1140 5400 5425 5660 5627 5027 4527 3827 2807 356.58 1457 1740 1560 962 337 -61.8
7 Fr Ra Rf Db Sg Bh Hs Mt Uun Uuu Uub
7 677 1737 ? ? ? ? ? ? ? ? ?

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
3469 3257 3127 3127 ? 1900 1597 3233 3041 2562 2720 2510 1727 1466 3315
Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
3200 4790 ? 3818 3902 3235 2607 ? ? ? ? ? ? ? ?
3
Phase Diagrams- Introduction
  • The effect of temperature and pressure on a
    substance in a closed container.
  • Every point represents a possible combination of
    temperature and pressure for the system.
  • Three areas represent the solid, liquid, and
    gaseous states of the substance.

4
  • Along AB line rate at which solid sublimes to
    form a gasrate at which gas condenses to form a
    solid
  • Along BC line rate at which liquid boils to form
    a gasrate at which gas condenses to form a
    liquid
  • Along BD line rate at which solid melts to form
    a liquidrate at which liquid freezes to form a
    solid

5
The Clausius-Clapeyron Equation
The relationship between the temperature of a
liquid and its vapor pressure is not a straight
line. The vapor pressure of water, for example,
increases significantly more rapidly than the
temperature of the system. This behavior can be
explained with the Clausius-Clapeyron equation.


If we assume that Hvap does not depend on the
temperature of the system, the Clausius-Clapeyron
equation can be written in the following
integrated form where C is a constant.
6
Densities of Solid, Liquid, and Gaseous Forms of
Three Elements
Solid (g/cm3) Liquid (g/cm3) Gas (g/cm3)
Ar 1.65 1.40 0.001784
N2 1.026 0.8081 0.001251
O2 1.426 1.149 0.001429
7
PHASE DIAGRAMS
  • STUDY OF PHASE RELATIONSHIPS IMPORTANT IN KNOWING
    PROPERTIES OF MATERIALS
  • MAP OF TEMPERATURE, PRESSURE AND COMPOSITION
    BETWEEN PHASES IN EQUILIBRIUM IN A SYSTEM
  • GIBBS PHASE RULE
  • P F C
    2
  • Eg states of matter-
    gas, liquid and solid single phase
  • Liquid
    mixture- oil and water- 2 phases
  • In solid ,
    several phases depending on crystal structure
  • STUDY IMPORTANT IN ALLOYS
  • ALLOY- SUBSTANCE COMPOSED OF 2 OR MORE CHEMICAL
    ELEMENTS
  • MAIN CONSTITUENT- BASE METAL
  • AND OTHERS ALLOYING ELEMENTS

8
CLASSIFICATION
  • SINGLE COMPONENT- UNARY
  • TWO COMPONENT- BINARY
  • THREE COMPONENT- TERNARY,

  • QUARTERNARY ETC.
  • EQUILIBRIUM APPROACHED BY VERY SLOW
    HEATING/COOLING

9
COOLING CURVES
  • For pure metal or
    compound

TEMPERATURE
Cooling of Liquid
Latent heat of solidification given off during
freezing- At constant temperature
Freezing begins
Freezing ends
Liquid Solid
Cooling of solid
Liquid
Solid
TIME, log scale
10
COOLING CURVES
  • For Binary solid
    solutions

TEMPERATURE
Freezing with drop in temperature
TIME, log scale
11
  • For Binary solid solutions-
  • composition 2
    composition1

TEMPERATURE
Ts1
Ts2
Te1
Te2
TIME, log scale
12
Phase Rule
FUSION LINE ALMOST VERTICAL- VARIATION IN
PRESSURE NO EFFECT ON M.P. OF ICE
FUSION
WATER
ICE
Pressure
B
76cm
VAPORISATION
WATER VAPOUR
30 cm
SUBLIMATION
T
A
0
100
50
Temperature o C
13
  • At A , water vapour - 1 phase
  • At B , water and water vapour co exist -2
    phases
  • At T , ice, water and water vapour exist 3
    phases
  • At A
  • 1 F chemical compound H2O 2
  • F 2 . BIVARIANT
  • At B
  • 2 F 1 2, F 1 UNIVARIANT
  • At T
  • All three phases P 3, 3 F 1 2 F 0

  • INVARIANT

14
Equilibrium Diagram
  • Case 1
  • Binary Alloy with COMPLETE SOLUBILITY IN BOTH
    LIQUID AND SOLID PHASES in all compositions
  • Eg Ag-Au Cu-Ni Ge-Si Al2O3-Cr2O3
    Sb-Bi
  • Silver-Palladium Co-Ni Cu-Pt Fe-Pt
    Ni-Pt Ta-Ti
  • HUME ROTHERYS RULE-

FICKS LAWS OF DIFFUSION
FIRST LAW
SECOND LAW
15
Elements A and B in a Binary Alloy
Cooling Curves Phase Diagram
16
Phase (Equilibrium) Diagram
Liquidus curve
L a
Solidus curve
Composition, C ( wt of B)
17
LEVER RULE
  • With Fulcrum at P, weights WA and WB at the end
    of a lever, for equilibrium, the lever rule
    states

WA / WB b/a
WB
WA
P
a
b
18
Liquid
P1
P
X
Y
Liquid Solid
Solid
47.5
16
37
58
For P SS/LS (37-16)/(58-37) 1/1
For P1 SS/LS 31.5/ 10.5 3/1
19
Liquid
P1
P
X
Y
Liquid Solid
Solid
31.5/ 10.5 3
47.5
16
37
58
(37-16)/(58-37)
20
(No Transcript)
21
(No Transcript)
22
The structures shown are at NON EQUILIBRIUM
CONDITIONS
23
60 Ni, 40 Cu- Liquid Phase
Solid Solution, with L and S phases
Nickel Rich Solid Solution
24
At A 60/40 composition - SS formed as with B At
X, L a, a with SS B1, rich in Ni, LS rich in Cu
At B2 60/40 composition- SS formed as (60/40)
25
Liquidus
A
Solidus
Cu
Ni
Ni
60 Ni/40 Cu
26
TIE LINE
27
There are Three variables, one of these can be
chosen as independent
If fl and fs are the liquid and solid fractions,
28
At A 60/40 composition - SS formed as with B At
X, L a, a with SS B1, rich in Ni, LS rich in Cu
At B2 60/40 composition- SS formed as (60/40)
29
Case 2 Binary Alloy with COMPLETE SOLUBILITY IN
LIQUID STATE in all compositions, but COMPLETELY
INSOLUBLE IN THE SOLID STATE
  • A very doubtful situation in practice, since most
    solid metals appear to dissolve small quantities
    of other metals
  • In Bismuth-Cadmium, mutal solid solubility is
    negligible.
  • Bi- heavy, brittle- positioned near to non metals
    in periodic table- Rhombic type
    structure-covalent bond
  • Cadmium- HCP-

30
Bismuth- Cadmium Equilibrium Diagram
31
When two metals show complete solubility in
liquid state, and complete insolubility in the
solid state,they do so by crystallising out as
alternate layers of the two pure metals. This
laminated structure termed as EUTECTIC
Te
40Cd/60Bi
32
When two metals show complete solubility in
liquid state, and complete insolubility in the
solid state, they do so by crystallising out as
alternate layers of the two pure metals. This
laminated structure termed as EUTECTIC
INVARIANT REACTION
Te (EUTECTIC Temperature)
40Cd/60Bi
33
At E, solid Cadmium (40) and solid Bismuth(60)
co-exist EUTECTIC
A Molten homogeneous alloy 1 phase with 2
components, Bi and Cd 1F 2 1 (only
temperature is the variable, not pressure) , F2
  • B 2 F 2 1, F 1
  • C 3 F 2 1, F0

34
Eutectic is considered as an intimate mixture
of two metals
  • Phase Rule applied, PF C 1
  • 3 F 2 1, F 0

35
Cooling curve for Eutectic (similar to pure
metal)
36
For compositions to left /right of Eutectic
Temperature o C
Time
37
HUME ROTHERYS RULE
38
Gold- Silver, Copper- Nickel, Germanium-
Silicon, Antimony- Bismuth, Aluminium Oxide-
Chromium Oxide etc. are examples
39
FICKS LAWS OF DIFFUSION
  • Mass Flow Process by which atoms (molecules)
    change their positions relative to their
    neighbours in a given phase under the influence
    of thermal energy and gradient

40
FICKS LAWS OF DIFFUSION
41
FIRST LAW
dn/dt no. of moles of B atoms crossing per unit
time D Diffusion coefficient A Planar
area dc/dx concentration gradient If J flux
flow / unit area per unit time,
42
SECOND LAW
If D is independent of concentration,
43
INVARIANT REACTIONS
44
Case 3 Two metals completely soluble in all
proportions in liquid state, but partially
soluble in solid state
  • Melting Point of Lead3270C
  • Melting Point of Tin 2320C
  • Eutectic Temperature 1830C
  • Eutectic Composition 62 Sn, 38Pb
  • Max. solid solubility tin in lead at 1830C 19.5
    tin
  • Max. Solid solubility of lead in tin at 1830C
    2.6 lead
  • Eutectic of two solid solutions a and ß (instead
    of two metals) form

45
Melting Point of Tin (Pb) 2320C
Melting Point of Lead (Sn) 3270C
Eutectic Temperature 1830C Eutectic
Composition 38Pb, 62 Sn Max. solid solubility
tin in lead at 1830C 19.5 tin Max. Solid
solubility of lead in tin at 1830C 2.6 lead
46
Liquid solubility of salt in water
partial solid solubility of one metal in
another- ( (similarity
schematically represented)
47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
About PowerShow.com