材料科学基础-课件 清华skja_11.ppt

1、材料科学基础Fundamental of Materials,Prof: Tian Min Bo Tel: 62795426 ，62772851 E-mail: Department of Material Science and Engineering Tsinghua University. Beijing 100084,Lesson eleven,3.10 Silicates,.Introduction Silicates are compounds that mainly composed of SiO4. It is the essential components of most

2、rock and soil, such as quartz, feldspar, mica etc.,.Features 1. Basic sell: SiO4 rsi/rO0.40/1.350.300.414,SiO44-,4,SiO4 tetrahedron,Si4+ is the cation that have small radii and large electrovalence.,The distance between Si and O: SiO : 1.6 (practical) 1.75 (theoretic),(0.40+1.35),2. The bonds of Si-

3、O-Si is not beeline but zigzag line. The angle of oxygen point is 145 in silicate. 3. For every oxygen, there is at most two SiO4 tetrahedrons can share it. 4. The SiO4 tetrahedrons can exist isolated or connect each other at common point.,5. In silicate structure: So, the CN of aluminum could be 4

4、or 6 6. The chemic expression or mineral. molecular formula : Al2O32SiO2H2O ; ZrO2SiO2 structural formula : Al2Si2O5(OH)4 ; ZrSiO4,aluminum + oxygen,aluminum-oxygen tetrahedrons,replace SiO4 tetrahedrons,aluminum-silicate,aluminum-oxygen octahedron,.Classification island chain (single, double) sheet

5、 (single, double) frame,1. Island silicates,Si:O=1:4,Si:O=1:3.5,Si:O=1:3,Si:O=1:3,Si:O=1:3,characteristic single: molecular formula: M4+SiO4、 M22+SiO4 typical minerals olivine, zircon, garnet,SiO4四面体及其硅氧团之间不共顶点相连，硅氧团被金属离子隔开形成孤立的岛状。,硅氧四面体还可以成对硅氧团出现，或成三方环状、四方环状或六方环状硅氧团出现，这些有限的硅氧团之间被金属阳离子隔开,双环 三环 四环 六环

6、,2. Chain silicates,single,characteristic 硅氧四面体通过共用两个或者两个以上的顶点，连接形成一向延长的链状结构。链与链之间被金属阳离子隔开。,single Si:O=1:3,typical minerals pyroxenes，CaMgSi2O6 , Mg2Si2O6,double,typical minerals tremolite ; (OH)6Mg6(Si4O11)H2O,double Si:O=4:11,3. Sheet silicates,Si:O=4:10,characteristic SiO4以三个以上的顶角相连形成在二维方向呈六角对称的

7、平面无限延伸的层状结构。,typical minerals,talc Mg3(OH)2Si4O10,muscovite KAl2(OH)2AlSi3O10,Kaolinite Al2(OH)4Si2O6,4. Frame silicates,Si:O=1:2,cristobalite,typical minerals cristobalite（silica SiO2）, feldspar,characteristic SiO4以其四个顶点在三维方向相连形成无限延伸的三维网络结构。,3.11 Summary,.Terminology: components , composition and i

8、ts description , phase , structure,.Classification:,solid solution,compounds (intermediate phase),substitutional ,interstitial ,primary or terminal ( it must be disordered ),intermediate or secondary ,ordered disordered ,normal valence ,electron ,size ,ionic : Paulings rule disordered : (8-N) rule,interstitial topological ,simple complex ,laves phases phases,silicates,island,chai