MATERIALS SCIENCE

MENJANA MINDA KREATIF DAN INOVATIF

What is materials science ?Relationship between structures and properties of

materials

Examples

1. Fe + C

+ Cr

Heat Treatment

2. Al + Si+ Heat treatment

SiC particles

Relates to the arrangements

of electrons surrounding of

the atom which influence the

atomic bonding

Introduction

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Properties are the way the material responds to the

environment and external forces

Mechanical Properties

Electrical & Magnetic

Properties

Thermal Properties

Optical Properties

Chemical Properties

Response to mechanical forces,

strength, etc

Response to electrical and magnetic

fields, conductivity, etc

Related to transmission of heat and

heat capacity

Include to absorption, transmission

and scattering of light

In contact with the environment eg :

corrosion resistance

Introduction

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Properties are the way the material responds to

the environment and external forces

Mechanical Properties :

Response to mechanical forces, such as

Strength (……….)

Toughness

Hardness

Ductility

Elasticity, Fatigue, Creep…etc

Introduction

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Important to understand capabilities and limitation

of materials

Lack of fundamental understanding of materials

and their properties will cause catastrophic failure

1

Why study Materials Science ?

Introduction

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An understanding of Materials Science helps us to design

better components, parts , devices, etc.

How do you make something stronger or lighter?

How do elements come together to form alloys ?

Why ……..

2

It is interesting and helps to make you more informed person3

Introduction

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There are 3 major classes

1. MetalStrong, ductile, High thermal & electrical conductivity, Opaque, reflective

Pure metallic elements or combination of metallic elements (alloys) .

Air frame, landing gear, engine components

2. CeramicBrittle, glassy, elastic, Non-conducting (insulators)

Molecules based on bonding between metallic and non-metallic elements. Typically insulating and refractory – coating on high temp engine components

3. PolymersDuctile, low strength, low density, Thermal & electrical insulatorsOptically translucent or transparent

Many are organic compound Chemically based on C , H other non-metals

– windows , cabin interior

Introduction

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Sub-classes of Materials

i. Semiconductor (ceramics), Intermediate electrical properties

ii. Composite (all three classes), combination

iii. Bio Materials (all three classes), Compatible with body tissue

Introduction

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Ceramics

Glass

Graphite

Diamond

Composites

PMC

MMC

CMC

Engineering Materials

Metals Non-Metals

Ferrous

Irons

Carbon Steel

Alloy Steel

…...

Non ferrous

Aluminium

Copper

Titanium

…...

Polymers

Thermoplastics

Thermosetting

Elastomers

Introduction

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Metal

Introduction

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CERAMIC

Introduction

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POLYMER

Introduction

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COMPOSITE

Introduction

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SEMICONDUCTOR

Introduction

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6

• Columns: Similar Valence Structure

THE PERIODIC TABLE

giv

e u

p 1

e-

giv

e u

p 2

e-

giv

e u

p 3

e- in

ert

ga

se

s

acce

pt 1

e-

acce

pt 2

e-

O

Se

Te

Po At

I

Br

He

Ne

Ar

Kr

Xe

Rn

F

ClS

Li Be

H

Na Mg

BaCs

RaFr

CaK Sc

SrRb Y

Introduction

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Introduction

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+Ceramic

Introduction

Metallic

elements

Non-metallic

elements+

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Introduction

Polymer

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Introduction

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. Introduction

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Angstrom = 1Å = 1/10,000,000,000 meter = 10-10m

Nanometer = 10nm = 1/1,000,000,000 meter = 10-9m

Micrometer = 1μm = 1/1,000,000 meter = 10-6m

Millimeter = 1mm = 1/1,000 meter = 10-3m

Atoms

= nucleus (protons and neutron)

+ electrons

Electrons, protons have negative and

positive charges of the same magnitude

Neutron are electrically neutral

Atomic Structure

Proton and neutron have the same mass

1.67 x 10 –27 kg

Mass of an electron is much smaller (9.11x

10 –31 kg and can be neglected in

calculation

The atomic mass (A) = mass of proton mass of neutron

Atomic number (Z) = number of proton

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The atomic mass unit(amu) is often used to express atomic weight.

The number of atom in a mole is called the Avogadro number, (Nav),

Nav = 6.023 x 10 23 Nav = 1 gram/amu

Example : Atomic weight of iron =55.85 amu/atom = 55.85 g/mol

Atomic Structure

Valence electrons – those in unfilled shells

Valence electrons determine all of the following

properties :

Chemical, Electrical, Thermal , Optical

Filled shells more stableValence electrons are most available for bonding and tend to control the chemical properties, etc..

Valence electrons

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1. Ionic bonding

Strong interaction among

negative atom (have an extra

electron ) and positive atom

(lost an electron)

Strong atomic bonds due to

transfer of electrons

2. Covalent bonding

Electrons are shared between

the molecules to saturate the

valence

Large interactive force due to

sharing of electrons

3. Metallic bonding

The atoms are ionized, loosing some electrons from the valence

band.

Those electrons form a electron sea, which binds the charged

nuclei in place.

Atomic Bonding

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• Occurs between + and - ions.

• Requires electron transfer.

• Large difference in electronegativity required.

• Example: NaCl

1. Ionic Bonding

Ionic bond : Metal + Non-metal

donates accepts electrons

electrons

Atomic Bonding

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3s1

3p6

Sodium

Atom

Na

Chlorine

Atom

Cl

Sodium Ion

Na+

Chlorine Ion

Cl -

I

O

N

I

C

B

O

N

D

Ionic bonding in NaCl

Atomic Bonding

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• Predominant bonding in Ceramics

He -

Ne -

Ar -

Kr -

Xe -

Rn -

F 4.0

Cl 3.0

Br 2.8

I 2.5

At 2.2

Li 1.0

Na 0.9

K 0.8

Rb 0.8

Cs 0.7

Fr 0.7

H 2.1

Be 1.5

Mg 1.2

Ca 1.0

Sr 1.0

Ba 0.9

Ra 0.9

Ti 1.5

Cr 1.6

Fe 1.8

Ni 1.8

Zn 1.8

As 2.0

CsCl

MgO

CaF2

NaCl

O 3.5

EXAMPLES: IONIC BONDING

Atomic Bonding

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Electrons are shared between the molecules to saturate the

valence

2. Covalent Bonding

H + H H H

1s1

Electrons

Electron

Pair

Hydrogen

Molecule

H

Atomic Bonding

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Requires shared electrons

Example : CH4

C : has 4 valence e, needs 4 more

H : has 1 valence e, needs 1 more

Atomic Bonding

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Si with electron valense : 4

Four covalent bonds must be formed

He -

Ne -

Ar -

Kr -

Xe -

Rn -

F 4.0

Cl 3.0

Br 2.8

I 2.5

At 2.2

Li 1.0

Na 0.9

K 0.8

Rb 0.8

Cs 0.7

Fr 0.7

H 2.1

Be 1.5

Mg 1.2

Ca 1.0

Sr 1.0

Ba 0.9

Ra 0.9

Ti 1.5

Cr 1.6

Fe 1.8

Ni 1.8

Zn 1.8

As 2.0

SiC

C(diamond)

H2O

C 2.5

H2

Cl2

F2

Si 1.8

Ga 1.6

GaAs

Ge 1.8

O 2.0

co

lum

n I

VA

Sn 1.8

Pb 1.8

EXAMPLES: COVALENT BONDING

Atomic Bonding

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Arises from a sea of donated valence

electrons (1, 2, or 3 from each atom).

Primary bond for metals and their alloys

3. Metallic Bonding

Atomic Bonding

Valence electrons are detached from

atoms, and spread in an electron sea that

“glues’ the ions together

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• Pure metals are significantly more malleable than ionic or covalent

networked materials.

• Strength of a pure metal can be significantly increased through

alloying.

• Pure metals are excellent conductors of heat and electricity.

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Levels of atomic arrangements in materials

1. Gas 2. Water 3. glass

3. Solid metal or alloy

- crystal

Crystalline Solid

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Crystalline SiO2

Non- crystalline SiO2

• atoms pack in periodic, 3D arrays

Crystalline materials

-metals

-many ceramics

-some polymers

• typical of:

• atoms have no periodic packing

Non-crystalline materials...

-complex structures

-rapid cooling

"Amorphous" = Noncrystalline

• occurs for:

Crystalline Solid

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How do atoms arrange themselves to form solid?

Crystal structure (microstructure) affects the mechanical

properties of materials such as tensile strength, ductility..etc

Crystal structure is describe as:

i. lattice : a 3-D of point in space. Each point must have identical

surrounding.

ii. Unit cell : the simplest repeating unit in a lattice

Crystal Structure

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•

• Unit cell : block of

atoms which repeats itself

to form space lattice.

Crystal structure : Atoms arranged in

repetitive 3-D pattern, in long range order

(LRO)

Properties of solids depends upon crystal

structure and bonding force.

Space lattice :

An imaginary network of lines,

with atoms at intersection of lines,

representing the arrangement of

atoms is called.

Crystal Structure

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Assume atoms as being hard spheres with

well-defined radii

The unit cell is the smallest

structural unit or building block

than can describe the crystal

structure.

Repeating of the unit cell generates

the entire crystal

a = Lattice parameter or lattice

constant

Crystal Structure

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7 crystal systems

14 crystal lattices

Unit cell: Smallest repetitive volume which contains the

complete lattice pattern of a crystal.

a, b, and c are the lattice constants

Crystal Structure

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Bravais Lattice : 7 crystal systems give 14 lattice

Only 7 different types of unit cells are necessary to create all point

lattices.

According to Bravais (1811-1863) 14 standard unit cells can describe

all possible lattice networks

1. Cubic

2. Tetragonal

3. Hexagonal

4. Orthorombic

5. Rhombohendral

6. Monoclinic

7. Triclinic

Crystal Structure

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1. Cubic Unit Cell a = b = c

α = β = γ = 900

ii. Simpleiii. Body Centered

i. Face centered

i. Simpleii. Body Centered

2. Tetragonala =b ≠ c

α = β = γ = 900

Crystal Structure

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3. Orthorhombic a ≠ b ≠ c

α = β = γ = 900

ii. Simple

iii. Base Centered

i. Face Centerediv. Body Centered

Simple

4. Rhombohedrala =b = c

α = β = γ ≠ 900

Crystal Structure

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5. Hexagonal a ≠ b ≠ c

α = β = γ = 900

6. Monoclinic a ≠ b ≠ c

α = β = γ = 900

7. Triclinic a ≠ b ≠ c

α = β = γ = 900

Simple

Simple

i. Simple ii. Base Centered

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Crystal Structure

Most of engineering metals have one of the following

crystal structure

i. Body-centered cubic (BCC)

ii. Face-centered cubic (FCC)

iii. Hexagonal close packed (HCP)

Crystal Structure

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1. Face-Centered Cubic (FCC)

Atoms are located at each of the corners and on the centers of all the

faces of cubic unit cell

Cu, Al, Ag, Au, Pb, Ni, Pt, ….. have this crystal structure

Good ductility

FCC

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Number of atoms per unit cell, n = 4

Fraction of volume occupied by hard sphere,

APF = 0.74

FCC

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2. Body-Centered Cubic (BCC)

Atom at each corner and at center of cubic unit cell

Cr, Fe-, Mo, Li, W have this crystal structure

BCC

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BCC

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a

a2

a3

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3. Hexagonal Close-Packed (HCP)

Atom at each corner and at center of unit cell

Be, Cd, Co, Mg, Ti, Zn have this crystal structure

HCP

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Crystal Structure

APF for a body-centered cubic structure

68.032.12

373.83

3

R

R

aR

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APF for a Face-centered cubic

74.0216

3

16

3

3

R

R

V

V

c

s

a

Crystal Structure

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APF for a Hexagonal Close-Pack

APF

= 0.74

r n A

VcNA

atoms/unit cell Atomic weight (g/mol)

Volume/unit cell

(cm3/unit cell)

Avogadro's number

(6.023 x 1023 atoms/mol)

THEORETICAL DENSITY,

Crystal Structure

r

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Element Aluminum Argon Barium Beryllium Boron Bromine Cadmium Calcium Carbon Cesium Chlorine Chromium Cobalt Copper Flourine Gallium Germanium Gold Helium Hydrogen

Symbol Al Ar Ba Be B Br Cd Ca C Cs Cl Cr Co Cu F Ga Ge Au He H

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Crystal Structure