清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 3.10 Silicates

33 10 Silicates . Introduction Silicates are compounds that mainly composed of [SiO4 It is the essential components of most rock and soil, such as quartz, feldspar, mica etc

§3.10 Silicates ◆ Ⅰ.Introduction Silicates are compounds that mainly composed of [SiO4 ]. It is the essential components of most rock and soil, such as quartz, feldspar, mica etc

I Features 1. Basic sell: [SIo4l rro=0.40/1.35=0.30<0.414 4 [Si04]4 Sioa tetrahedron

◆ Ⅱ.Features 1. Basic sell: [SiO4 ] rsi/rO＝0.40/1.35＝0.30<0.414 [SiO4] 4- 4－ SiO4 tetrahedron

Si+ is the cation that have small radii and large electrovalence The distance between si and o Si-O: 1.6 A(practical)<1.75 A(theoretic (0.40+1.35)

Si4+ is the cation that have small radii and large electrovalence. The distance between Si and O: Si－O : 1.6 Å(practical) < 1.75 Å (theoretic) (0.40+1.35)

2. The bonds of Si-o-Si is not beeline but zigzag Ine The angle of oxygen point is 1450 in silicate 3. For every oxygen, there is at most two SIO4 tetrahedrons can share it 4. The sio tetrahedrons can exist isolated or connect each other at common point

2. The bonds of Si-O-Si is not beeline but zigzag line. The angle of oxygen point is 145º 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 replace SIO4 aluminum-oxygen tetrahedrons aluminum-silicate aluminum oxygen aluminum-oxygen So, the cn of aluminum could be 4 or 6 6. The chemic expression or mineral molecular formula: AL2O3 2SiO2 H,O, Zro2 SiO2 structural formula: AL2SiO5(OH)4, Zrlsio

5. In silicate structure: So, the CN of aluminum could be 4 or 6 6. The chemic expression or mineral. molecular formula : Al2O3·2SiO2·H2O ; ZrO2·SiO2 structural formula : Al2 [Si2O5 ](OH)4 ; Zr[SiO4 ] aluminum + oxygen aluminum-oxygen tetrahedrons replace SiO4 tetrahedrons aluminum-silicate aluminum-oxygen octahedron

Classification island chain(single, double sheet(single, double) frame

◆ Ⅲ.Classification island chain (single, double) sheet (single, double) frame

1. Island silicates Si:O=1:4 Si:O=1:3.5 S:O=1:3 Si:O=1:3 S:O=1:3

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 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。 双环 环 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 四环 有限的硅氧团之间被金属阳离子隔开 六环 molecular formula M4SO4、M21sO4 typical minerals olivine, Zircon, garnet

➢ characteristic single: ➢ molecular formula: M4 + [SiO4 ]、 M2 2+ [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

2 Chain silicates 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 向延长的链状结构。链与链之间被金属阳离子隔开 single

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

[SiO3]2- single Si:O=1:3 typical minerals pyroxenes, CaMg[Sio6, Mg2Si2O61

single Si:O=1:3 ➢ typical minerals pyroxenes，CaMg[Si2O6 ] , Mg2 [Si2O6 ]