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chap3_10 - 材材材材材材 Fundamental of Materials Prof...

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Unformatted text preview: 材材材材材材 Fundamental of Materials Prof: Tian Min Bo Tel: 62795426 材 62772851 E-mail: [email protected] Department of Material Science and Engineering Tsinghua University. Beijing 100084 Lesson eleven §3.10 Silicates §3.10 Ⅰ.Introduction Silicates are compounds that mainly composed of [SiO4]. It is the essential composed. components of most rock and soil, such as quartz, feldspar, mica etc. quartz, Ⅱ.Features 1. Basic sell: [SiO4] 1. rsi/rO 材 0.40/1.35 材 0.30<0.414 4- [SiO4]4- SiO4 tetrahedron Si4+ is the cation that have small radii and large electrovalence. The distance between Si and O: Si 材 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 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 4. connect each other at common point. connect 5. In silicate structure: 5. aluminum + oxygen aluminum-oxygen tetrahedrons replace SiO4 tetrahedrons aluminum-silicate aluminum-oxygen octahedron So, the CN of aluminum could be 4 or 6 6. The chemic expression or mineral. molecular formula : Al2O3·2SiO2·H2O ; ZrO2·SiO2 molecular structural formula : Al2[Si2O5](OH)4 ; Zr[SiO4] structural Ⅲ.Classification island chain (single, double) sheet (single, double) frame 1. Island silicates Island Si:O=1:4 Si:O=1:3 Si:O=1:3.5 Si:O=1:3 Si:O=1:3 characteristic characteristic single: [SiO4] ----------------------------------- -- -- -- -- ------------------------------------------------------- - molecular formula: molecular M4+[SiO4] 材 M22+[SiO4] typical minerals olivine, zircon, garnet 2. Chain silicates Chain characteristic 材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材 single single single Si:O=1:3 typical minerals pyroxenes 材 CaMg[Si2O6] , Mg2[Si2O6] double double double Si:O=4:11 typical minerals tremolite ; (OH)6Mg6(Si4O11)·H2O tremolite 3. Sheet silicates 3. characteristic [SiO4] 材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材材 Si:O=4:10 typical minerals talc muscovite Kaolinite Mg3[(OH)2Si4O10] KAl2[(OH)2AlSi3O10] Al2[(OH)4Si2O6] 4. Frame silicates 4. Si:O=1:2 characteristic [SiO4] 材材材材材材材材材材材材材材材材材材材材材材材材材材材 typical minerals cristobalite 材 silica SiO2 材 , feldspar cristobalite cristobalite §3.11 Summary §3.11 Types Features [SiO4] 材材材材材材材材材材材材材 [SiO 材材材材材材材材材材材材材材材材材材材材材材材材 材材材材材材材材材材材 Structures Si:O 4− 1:4 [SiO 4 ]4− 4− 6− [Si 2 O17 ] 1 Island [Si 3O9 ]6− 材材材材材材材材材材材材材材材材材材材材材 材材材材材材材材材材材材材材材材材材材材材 材材材材材材材材材材材材材材材材材材材材材材材材 材材材材材材材材材材材 Examples 1:3.5 材材材 Zr[ SiO4 ] 材材材材 Mg 2 [SiO 4 ] 材材材 1:3 [Si 4 O12 ]8− 1:3 [Si 6 O18 ]12− 1:3 + R 3 2 R +3 [SiO 4 ]3 2 材材材材材 Y3+2 Al+3[SiO 4 ]3 2 Types Types Features Structures Si:O [SiO 3 ]2− 2 Chain 材材材材材材材材材材材材材材材材材材材材材 材材材材材材材材材材材材材材材材材材材材材 材材材材材材材材材材材材材材材材材材材材材材材材 材材材材 Examples 1:3 材材 R 2 [Si 2 O 6 ] [Si 4 O11 ]6− 4:11 材材材 Ca 2 Mg 5 [Si 4 O11 ]2 ( OH ) 2 3 Sheet [SiO4] 材材材材材材材材材材材材材 [SiO 材材材材材材材材材材材材材材材材材材材材材材 材材材 [Si 4 O10 ] 4− 4:10 材材 材材 4 [SiO4] 材材材材材材材材材材材材材材 Frame 材材材材材材材材材材材材材 SiO 2 1:2 1:2 材材 材材 Ⅰ.Terminology: components , composition and its description , phase , structure phase Ⅱ.Classification: substitutional ~ solid solution interstitial ~ primary ~ or terminal ~ ( it primary must be disordered ) must intermediate ~ or secondary ~ normal valence ~ compounds (intermediate phase) electron ~ ordered ~ disordered ~ ionic ~: Pauling's rule disordered ~: (8-N) rule r simple ~ B < 0.59 rA interstitial ~ size ~ island chain topological ~ silicates sheet frame glass metal glass amorphous glass ceramics ceramic glass rB complex ~ r ≥ 0.59 A laves phases δ phases Ⅲ.Features Examples and Discussions Examples Exercise Exercise Thank you ! Thank you ! 11 ...
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