에너지신소재공학 재료분석
- 최초 등록일
- 2012.05.27
- 최종 저작일
- 2012.01
- 25페이지/ MS 파워포인트
- 가격 1,000원
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본문내용
typical neighbor
bond energy
typical neighbor
bond length
? atoms pack in periodic, 3D arrays
Crystalline materials...
metals, many ceramics, some polymers
? atoms have no periodic packing
Noncrystalline materials...
-complex structures
-rapid cooling
crystalline SiO2
noncrystalline SiO2
"Amorphous" = Noncrystalline
Materials and Packing
Si
Oxygen
3.3. Unit cell(단위정)
: smallest repetitive volume which contains the complete lattice pattern of a crystal.
a, b, and c are the lattice constants
3.4 Metallic Crystal Structures
How can we stack metal atoms to minimize empty space?
2-dimensions
? Tend to be densely packed.
? Reasons for dense packing:
- Typically, only one element is present, so all atomic
radii are the same.
- Metallic bonding is not directional.
- Nearest neighbor distances tend to be small in
order to lower bond energy.
- Electron cloud shields cores from each other
? Rare due to low packing denisty (only Po has this structure)
? Close-packed directions are cube edges.
? Coordination # = 6
(# nearest neighbors)
Simple Cubic Structure (SC)
Atomic Packing Factor (APF : 원자 충진율)
APF =
참고 자료
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