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Ceramic Materials 陶瓷材料• Inorganic materials 無機材料• Nonmetallic materials 非金屬材料• Most ceramics are compounds between
metallic and nonmetallic elements
• Composed of at least two elements, and often more
• Atomic bonding in ceramics ranges from purely ionic to totally covalent
2
2ionic character 1A BX X
e
Material Ionic Character
CaF2 89%
MgO 73%
NaCl 67%
Al2O3 63%
SiO2 51%
Si3N4 30%
ZnS 18%
SiC 12%
Stable and unstable cation-anion coordination configuration
- -
- -+
unstable
- -
- -+
stable
- -
- -+
stable
Cations are ordinarily smaller than anionscation 陽離子 anion 陰離子
Coordination Number 配位數
2 3 4 6 8
Coordination Number 配位數
Cation-Anion Radius Ration rC/rA
<0.155 0.155-0.225 0.225-0.414 0.414-0.732 0.732-1
Crystal Structures• AX Type
– Rock Salt Structure 岩鹽結構– Cesium Chloride Structure 氯化銫結構– Zinc Blende (Sphalerite) Structure 閃鋅礦結構
• AX2 Type– Fluorite Structure 螢石結構、氟石結構
• ABX3 Type– Perovskite Structure 鈣鈦礦結構
• AB2X4 Type– Spinel Structure 尖晶石結構
Interstitial position填隙位置、間隙位置
• Tetrahedral position 四面體位置• Octahedral position 八面體位置
close-packed structure 最密堆積結構、緊密堆積結構
Crystal structure
• Hexagonal Close-Packed (HCP)
六方最密堆積– ABAB... Stacking Sequence
• Face-Centered Cubic (FCC)
面心立方– ABCABC... Stacking Sequence
c
a
A sites
B sites
A sites
ABC
Determine Crystal Structures
1. Stoichiometry 化學計量 Charge Neutrality
2. Cation-anion radii ratios (coordination number)
3. Covalent character
Ceramic Density Computation
A
AC
NV
)AA(n
C
Number of formula units/unit cell
AC: atomic weight of cation AA: atomic weight of anion VC: Volume of unit cellNA: Avogadro’s number
Silica 矽石、二氧化矽• Crystalline structure of Silica
– Quartz 石英– Cristobalite (Crystobalite) 白矽石、方矽石– Tridymite 鱗石英、鱗矽石
• The strong Si-O bond leads to a strong, high melting temperature (1710C)
Silica Glass 矽石玻璃• fused silica or vitreous silica 熔凝矽石或玻化矽石
• B2O3 and GeO2
– Network former
• CaO and Na2O– Network modifier
• TiO2 and Al2O3
– Intermediate
• Modifiers and Intermediates lowers the melting point and viscosity of a glass
Layered Silicates
• Can change the counterions ( 相對離子 )– this changes layer spacing– the layers also allow absorption of water
• Mica 雲母 KAl3Si3O10(OH)2
• Bentonite 膨土、火山黏土– used to seal wells– packaged dry
– swells 2-3 fold in H2O
– pump in to seal up well so no polluted ground water seeps in to contaminate the water supply
Carbon 碳• Diamond 鑽石
– metastable state 介穩態、準穩態• Graphite 石墨• Fullerene 芙、芙樂、富勒、芙樂烯、富勒烯
• C60
– Buckminsterfullerenes 巴克明斯特芙樂烯 – Buckyball 巴克球
Imperfections in Ceramic • Imperfection 缺陷• Electroneutrality 電中性• Atomic Point Defect
– Vacancy 空位– Interstitial 填隙、間隙
• Defect Structure– Frenkel defect 夫倫克耳缺陷– Schottky defect 肖特基缺陷
• Stoichiometry or Nonstoichiometry
Impurities in Ceramics
• Electroneutrality 電中性• Solid solution 固溶體
– substitutional type– interstitial type
Diffusion in Ionic Materials
• Diffusion in ionic materials usually occurs by a vacancy mechanism
• Electroneutrality 電中性
Brittle Fracture of Ceramics
• brittle fracture 脆性斷裂• plastic deformation 塑性形變• fractography 斷口形像學• crack 裂痕、裂紋、裂縫• branch or bifurcate 分叉
Stress-Strain Behavior
• Stress 應力• Strain 應變• flexural strength 抗彎強度、抗撓強度、撓曲強度
• modulus of rupture 破壞模數 • fracture strength 破裂強度 • bend strength 彎曲強度
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