Materials Camp 2010

8/3/2019 Materials Camp 2010

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Introduction to Materials

Science and Engineering


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Materials Science Investigating

relationships that exist between the

structure and properties of materials

Materials Engineering Is, on the basis of

these structure-property correlations,designing or engineering the structure of a

material to produce a pre-determined set of

properties

Branch of engineering which deals with the

study of engineering usefulness of solid

materials.


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Structure

Sub atomic electrons and nuclei (protonsand neutrons)

Atomic organization of atoms or molecules

Microscopic groups of atoms that are

normally agglomerated together

Macroscopic viewable with the un-aided

eye


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Uses of Composites

Composite Banjo

Composite Guitar

Composite Piccolo

Composite Shoes


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Uses of Composites

Composite BaseballBat from Miken Sports


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Uses of Composites

Graphite Snowboard

Composite Bicycle

LaminatedFiberglass Bow


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MATERIAL SCIENCE & ENGINEERING IN A NUT SHELL


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Many engineering materials have

structure sensitive propertiesdepending on presence or absence ofimperfections.

Imperfections volume fraction may beas small as 0.01% BUT their effect is

very tremendous on someproperties.


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Structure insensitive

properties

Elastic modules

Density

Melting point

Specific heat

Co-efficient of

thermal expansion

Structure sensitive

properties

Electrical

conductivity

Semi-conductive

phenomena

Yield strength

Fracture strength

Creep strength


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METALLIC CRYSTALS


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Space lattice


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12/14/2011 Slide 3 (of 31)

So what is a Space lattice ?

3D regular arrangement of points in space

How can the atomic arrangement in solidsbe mathematically described?


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12/14/2011 Slide 4 (of 31)

Lattice parameters

To define any lattice 6 lattice parameters are

needed:

a, b, c as (sides) & a, b, g (angles)

How many unique space lattices can be

derived?

Only 7 such lattices can be derived

C t l t


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Crystal systems


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Slide 8 (of 31)

Crystal systems Seven crystal systems

Fourteen Bravais lattices Cubic and Hexagonal systems: 90% of all

metals have a cubic or hexagonal structure


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Bravais lattice


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Slide 10 (of 31)

Crystal

structures

or

14 Bravais

lattice


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5

Rare due to poor packing (only Po has this structure)

Close-packed directions are cube edges.

Coordination # = 6

(# nearest neighbors)

(Courtesy P.M. Anderson)

SIMPLE CUBIC STRUCTURE (SC)


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6

APF for a simple cubic structure = 0.52

Adapted from Fig. 3.19,

Callister 6e.

ATOMIC PACKING FACTOR

BODY CENTERED CUBIC


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Coordination # = 8

7

Adapted from Fig. 3.2,Callister 6e.


Close packed directions are cube diagonals.

--Note: All atoms are identical; the center atom is shadeddifferently only for ease of viewing.

BODY CENTERED CUBIC

STRUCTURE (BCC)


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aR

8

APF for a body-centered cubic structure = 0.68

Unit cell c ontains:

1 + 8 x 1/8

= 2 atoms/unit cell

Adapted fromFig. 3.2,Callister 6e.

ATOMIC PACKING FACTOR: BCC

FACE CENTERED CUBIC


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Coordination # = 12

Adapted from Fig. 3.1(a),Callister 6e.


Close packed directions are face diagonals.

--Note: All atoms are identical; the face-centered atoms are shadeddifferently only for ease of viewing.

FACE CENTERED CUBIC

STRUCTURE (FCC)


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Unit cell c ontains:

6 x 1/2 + 8 x 1/8

= 4 atoms/unit cell

a

10

APF for a body-centered cubic structure = 0.74

Adapted fromFig. 3.1(a),Callister 6e.

ATOMIC PACKING FACTOR: FCC


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ABCABC... Stacking Sequence

2D Projection

A sites

B sites

C sitesB B

B

BB

B BC C

CA

A

FCC Unit Cell

FCC STACKING SEQUENCE

HEXAGONAL CLOSE PACKED


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12

Coordination # = 12

ABAB... Stacking Sequence

APF = 0.74

3D Projection 2D Projection

A sites

B sites

A sites

Adapted from Fig. 3.3,

Callister 6e.

HEXAGONAL CLOSE-PACKED

STRUCTURE (HCP)


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Compounds: Often have similar close-packed structures.

Close-packed directions--along cube edges.

Structure ofNaCl

(Courtesy P.M. Anderson) (Courtesy P.M. Anderson)

STRUCTURE OF COMPOUNDS: NaCl


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(c)2003Brooks/ColePublishing/ThomsonLearning


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Useful up to 2000X magnification.

Polishing removes surface features (e.g., scratches)

Etching changes reflectance, depending on crystalorientation.

close-packed planes

micrograph ofBrass (Cu and Zn)

Adapted from Fig. 4.11(b) and (c), Callister6e. (Fig. 4.11(c) is courtesyof J.E. Burke, General Electric Co.

0.75mm

OPTICAL MICROSCOPY (1)


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Grain boundaries...

are imperfections,

are more susceptible

to etching,

may be revealed as

dark lines, change direction in a

polycrystal.Adapted from Fig. 4.12(a)and (b), Callister 6e.(Fig. 4.12(b) is courtesyof L.C. Smith and C. Brady,

the National Bureau ofStandards, Washington, DC[now the National Institute ofStandards and Technology,Gaithersburg, MD].)

OPTICAL MICROSCOPY (2)

The new era of Nanotechnology is coming


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The new era of Nanotechnology is coming

www.n a n o r o b o t d e s i g n.com www.c a n b i o t e c h n e m s.com


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Nanotechnology deals with the creation ofUSEFUL materials, devices and systems

through

control of matter on the nanometer length scaleand exploitation of

NOVEL phenomena and properties

(physical, chemical, biological)at that length scale

H ll i t ? ( d th ll i )


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Start with a centimeter.

Now divide it into 10 equal parts.

Now divide that into 10 equal parts.

Now divide that into 100 equalparts.

Now divide that into 10 equal parts.

Finally divide that into 100 equalparts.

A centimeter is about the size of a bean.

Each part is a millimeter long. About thesize of a flea.

Each part is 100 micrometers long.About the size (width) of a human hair.

Each part is a micrometer long. Aboutthe size of a bacterium.

Each part is a 100 nanometers long.About the size of a virus.

Each part is a nanometer. About the size

of a few atoms or a small molecule.

How small is a nanometer? (and other small sizes)

1 cm

1 mm

100 mm

1 mm

100 nm

1 nm


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The Nanometer Size Scale

Nanotube


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Why is Small Good?

- Faster

- Lighter

- Can get into small spaces

- Cheaper

- More energy efficient

- Different properties at very small scale


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Documents

Materials Camp 2010