© GNU Su-Jin Kim

Crystaline Solid

Material Science

Crystalline Solids(고체의결정구조)

Associate Professor Su-Jin Kim

School of Mechanical Engineering

Gyeongsang National University

© GNU Su-Jin Kim

Crystaline Solid

Material Science

OCW

• Solids: Amorphous, Crystalline[Atomic(Metallic, Network), Ionic, Molecular] : https://youtu.be/bzr-byiSXlA or https://youtu.be/Ugd-O8Rl-xo

• Solids : Amorphous, Crystalline, Polycrystalline https://youtu.be/9hZonAufaK8 or https://youtu.be/KaJfI3IjcA0

© GNU Su-Jin Kim

Crystaline Solid

Material Science

KOCW

결정질고체의구조1

http://www.kocw.net/home/cview.do?lid=e3b3aa8d5f4fe457

결정질고체의구조2

http://www.kocw.net/home/cview.do?lid=73a944a210fcc2ff

결정질고체의구조 3

http://www.kocw.net/home/cview.do?lid=ac01572fd22d54c9

© GNU Su-Jin Kim

Crystaline Solid

Material Science

Cristal Structure

• Atoms (assume hard spheres) are packed BCC, FCC, HCP structures

• Atomic Packing Factor, APF (충진율) = Volume of atoms in unit cell / Volume of unit cell

• Theoretical density (밀도) = Mass of atoms in unit cell / Volume of unit cell

• Crystallographic planes(결정방향) are expressed by Miller indices. ex) (1 0 0)

4

© GNU Su-Jin Kim

Crystaline Solid

Material Science

a

√3a

R

5

• Atoms touch each other along cube diagonal corners.

• Fe, Cr, W

Body Centered Cubic, BCC (체심입방)

2 atoms / unit cell

© GNU Su-Jin Kim

Crystaline Solid

Material Science

4 atoms / unit cell

6

• Atoms touch each other along face diagonals.

• Al, Cu, Pb, Ni, Au, Pt, Ag

Face Centered Cubic, FCC (면심입방)

AFP = 0.74

© GNU Su-Jin Kim

Crystaline Solid

Material Science 7

• Hexagon-Triangle-H-T… Stacking Sequence

• Mg, Ti, Zn, Cd

Hexagonal Close-Packed, HCP (육방조밀)

6 atoms/unit cell

Hexagon

Triangle

Hexagon

AFP = 0.74

© GNU Su-Jin Kim

Crystaline Solid

Material Science

Crystallographic Planes (결정방향)

• Miller Indices: Reciprocals of the (three) axial intercepts for a plane. Intercept(교차)Reciprocal(역수) Integer(정수) values

(110) (200) (211)

z

x

y

Diffraction angle 2q

X-ray diffraction pattern (X선회절) for polycrystalline a-iron (BCC)

Inte

nsity (

rela

tive

)

© GNU Su-Jin Kim

Crystaline Solid

Material Science

Single crystal, Polycrystalline, Amophous

• Single crystal(단결정)

• Polycrystalline(다결정)

• Amorphous (비정질)

Single crystal diamond

Cast iron grain

Glass

Metals, rock, salts

Glass, plastic, resin, sugar

© GNU Su-Jin Kim

Crystaline Solid

Material Science 10

Single crystals (단결정)

Material properties generally vary with single crystal

orientation. they are anisotropic(이방성).

Single crystal silicon wafer & anisotropic etching

(111)

© GNU Su-Jin Kim

Crystaline Solid

Material Science

Polycrystalline (다결정)

• Most engineering materials are polycrystalline.

• Each grain(결정립) is a single crystal.

• If grains are randomly oriented, overall component

properties are isotropic(등방성, not directional).

• Grain sizes typically range from 1 nm to 2 cm

liquid crystals grow

polycrystalline

grainsPolycrystalline

grains of metal

© GNU Su-Jin Kim

Crystaline Solid

Material Science 12

Atoms have no periodic packing

Transparent

ex) Glass

noncrystalline SiO2

Amorphous = Noncrystalline

Amorphous (비정질)

Si Oxygen

© GNU Su-Jin Kim

Crystaline Solid

Material Science

Summary

• Metallic crystal: FCC, BCC, HCP

• Single crystal: Anisotropic (properties vary with crystal orientation)

• Poly crystalline: Isotropic (properties are non directional randomly oriented grains)

• Amorphous: Isotropic (random)

© GNU Su-Jin Kim

Crystaline Solid

Material Science

Delete

5. Single Crystal, Polycrystalline, Amorphoushttps://www.youtube.com/watch?v=KaJfI3IjcA0&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm&index=5

Families of directions/planes

https://www.youtube.com/watch?v=5f4C6e-9rgg&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm&index=6

Crystallographic Points

https://www.youtube.com/watch?v=dP3LjWtoeMU&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm&index=7

Crystallographic Directions

https://www.youtube.com/watch?v=fYK45OdnZH0&index=9&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm

Atomic densities and Packing Factors

https://www.youtube.com/watch?v=RGCqLEU2IIM&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm&index=10

11. FCC structurehttps://www.youtube.com/watch?v=pHt7--8I4bQ&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm&index=11

Ionic crystal structures

https://www.youtube.com/watch?v=A3cPHn_OgVQ&list=PL8EAOgbez9XIWGbmcihctMO4bXSB4V8hm&index=12