imperfection in solids -...

Imperfection in solids

By Patama VisuttipitukulE-mail: [email protected]

Imperfection in Solids by Patama Visuttipitukul

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Solid

• Solid – State of materials – Rigid – Strong bonding – ionic, van der Waals , metal

bonding – normally has crystal structure


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Examples of Imperfections #1

Imperfection in solid


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Examples of Imperfections #2

distortion of planes

distortion of planes

Imperfection

Imperfection

Imperfection causes distortion of planes and abnormal arrangement of atoms. This affects properties of materials: mechanical, electrical properties and so on.


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Imperfection: Defect causes by an atom #1

This defect called “Vacancy”

Vacancy


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This defect called “SubstitutionalSolid Solution” (by a bigger atom)


Substitutional Solid Solution


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This defect also called “Substitutional Solid Solution”(by a smaller atom)

Imperfection: Defect causes by an atom#3

Substitutional Solid Solution


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This defect also called “Interstitial Solid Solution” (by a very small atom)

Imperfection: Defect causes by an atom#4

Space between atoms

Interstitial Solid Solution


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• Summary: defects cause by an atom could be:– Vacancy– Substitutional solid solution (by bigger or smaller

atoms)– Interstitial solid solution


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• Amount or number of “defect” found in crystal can be calculated by

Number of defect depends on Temperature.


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• Defect causes by an atom has no dimension or zero dimension !!

• It can be called “Point defect” .Remember that point defect is a defect causes by an atom (or

absence of atom) and it has zero dimension.

• There are other kinds of defects which have one, two or three dimensions (1D, 2D, 3D).

Note that :1D has only length (L)2D has length (L)*width(W)3D has length(L)*width(W)*depth(D)


LL

W

LW

DImperfection in Solids by Patama Visuttipitukul

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Note that :

1D has only length (L)2D has length (L)*width(W)3D has length(L)*width(W)*depth(D)

LL

W

LW

D

Imperfection: Line Defect


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Imperfection- Line defect #1

This type of dislocation is called “Edge dislocation” which can be considered as a line defect.

Perfect crystal

Perfect crystal

Extra plane

Line defect or

‘Dislocation’


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The “Screw dislocation” also can be considered as a line defect in materials


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Note that :1D has only length (L)

2D has length (L)*width(W)3D has length(L)*width(W)*depth(D)

LL

W

LW

D

Imperfection: Interfacial Defect


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Imperfection- Interfacial defect #1

Atom “A”

Atom “B”

Planar

DefectPlanar

Defect

“Planar defect” or “Interfacial defect” is a two-dimensions defect such as interface between two materials, grain boundary and so on.


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Imperfection- Interfacial defect #2


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Note that :1D has only length (L)2D has length (L)*width(W)

3D has length(L)*width(W)*depth(D)

LL

W

LW

D

Imperfection: Bulk Defect


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Imperfection- Bulk defect #1

Perfect crystal

Imperfection or “Defect” occurs

Defect is a three-dimensions defect (it has height, width and length).

Bulk defects can be impurities, hole, crack … which have three-dimensions.

H

W L


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Summary about imperfections

• Crack, Holes, Impurities Bulk defects

Interfacial defects


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Dislocation VS Mechanical properties #1


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Slip occurs in these plane


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Need low

force

Need higher force

Low dislocation density Deform easily High dislocation density Deform hardly


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Summary of Dislocation VS Mechanical properties


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Calculation of concentration


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• Other useful relationsCalculation of concentration

3

2

2

1

1

11 10" ×

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

+=

ρρCC

CC 3

2

2

1

1

21 10" ×

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

+=

ρρCC

CC

2

2

1

1

100

ρρ

ρ CCave

+=

2

22

1

11

2211

''''

ρρ

ρ ACACACAC

ave

+

+=

2

2

1

1

100

AC

ACAave

+=

100'' 2211 ACACAave

+=

Concentration in mass per unit volume (kg/m3)

Average density (kg/m3)

Average atomic weight

Note that: 1. these equations can be used for two element alloy.

2. C is concentration by weight (weight percent), C’ is concentration by atom(atomic percent).Imperfection in Solids by Patama Visuttipitukul

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Example in concentration calculation

• Al 94 g+ Cu 6 g– Calculate weight percent of Al and Cu– Calculate atomic percent of Al and Cu– Calculate concentration by mass per unit

volume– Calculate average density– Calculate average atomic weight


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Optical Microscope #1


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Optical Microscope #2

imperfection in solids -...

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