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Introduction to materials science and engineering

Atoms / electron configuration

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Bonding in solids

Structure of crystal solids

Bonding Forces and EnergiesBonding Forces and Energies

re p u ls iv e

a ttra c tiv e

n e t e n e rg y

e n e rg y /fo rc e

r 0

in te ra to m ic fo rc e

distance r

The Periodic TableThe Periodic Table

METALS NONMETALS

INTERMEDIATE

increasing electronegativity

Ionic Bonding Ionic Bonding Covalent Bonding Covalent Bonding

e.g. sodium chloride e.g. methane

Metallic BondingMetallic Bonding

+

d isc re te e n e rg y le v e ls o f e le c tro n sE

1

23

4

rn u c le u s+ +

1

2

n u c le u s

e n e rg y b a n d s = > fre e e le c tro n s

+

+

+

+

+

+

+

+

+ +

+ +

+ +

+ +

-

-

-

-

-

-

-

-

-

io n c o re s se a o f e le c tro n s

Bonding EnergiesBonding Energies

low

high

Crystalline StructuresCrystalline Structures

Crystalline StructuresCrystalline Structures

amorphous crystalline

Example: GlassExample: Glass

quartz(crystalline)

quartz glass(amorphous)

Si4+O2-

glass(amorphous)

Crystalline StructuresCrystalline Structures

simple cubicbody-centered cubic (bcc)

bcc

fcc

Hexagonal Crystal StructuresHexagonal Crystal Structures

hcp unit cell

Stacking Sequence of Stacking Sequence of Close-Packed StructuresClose-Packed Structures

first plane Afirst plane A and second plane Bfirst plane A, second plane B and third plane C: fccfirst plane A, second plane B and third plane A: hcp

FCC and BCC Solid Sphere ModelFCC and BCC Solid Sphere Model

fcc unit cell bcc unit cell

R

R = atomic radiusa = unit cell length / lattice constant

a a

Crystalline Structures of MaterialsCrystalline Structures of Materials

Lattice ParametersLattice Parameters

a

b

c

x

y

z

Crystal SystemsCrystal Systems

Crystal SystemsCrystal Systems

How to define a directionHow to define a direction

Vector of convenient length (pass through origin)

Project the vector to the axes (and measure in a, b, and c)

Multiply or divide these numbers by common factor to get smallest set of integers

Write them down as [uvw]

Miller Indices: Miller Indices: Crystallographic DirectionsCrystallographic Directions

a

b

c

x

y

z

a

b

c

x

y

z

Miller Indices: Crystallographic Miller Indices: Crystallographic Directions (Miller Bravais)Directions (Miller Bravais)

a 1

a 2

a 3

z

[0 001 ]

[111 0 ]

How to define a planeHow to define a plane

Plane may not include origin!

Determine the intercepts with appropriate axes as a, b, and c

Take reciprocals (no intercept means infinity reciprocal of infinity = 0)

Multiply or divide these numbers by common factor to get smallest set of integers

Write them down as (hkl)

Miller Indices: Miller Indices: Lattice PlanesLattice Planes

x

z

y

(0 11 )

x

z

y

= > (111 )

x

z

y

intersection points: 1/2 a, 1/2b, 1/2creciprocal values: (222)

DefectsDefects

Point defects

Linear defects

2-dimensional defects

Point DefectsPoint Defects

self-interstitial vacancy

Impurity AtomsImpurity Atoms

interstitial substitutional

Dislocations: Edge DislocationDislocations: Edge Dislocation

Burgers vectorinserted half plane

dislocation line

Dislocations: Screw DislocationDislocations: Screw Dislocation

Burgers vector

dislocationline

Grain BoundariesGrain Boundaries

Ni-Base Superalloy Waspalloy

50µm

high-angle grain boundary (>15°)

low-anglegrain boundary

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Properties of materials