材料科学基础第03章4

1、材料科学基础Fundamental of MaterialsLesson eleven3.10 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.Features 1. Basic sell: SiO4 rsi/rO0.40/1.350.300.414SiO44-4SiO4 tetrahedron Si4+ is t

2、he 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-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

3、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 or 66. The chemic expression or mineral. molecular formula : Al2O32SiO2H2O ; ZrO2SiO2 structural formula : Al2Si2O5(OH)4 ; ZrSiO4 aluminum + oxy

4、gen aluminum-oxygen tetrahedrons replace SiO4 tetrahedrons aluminum-silicate aluminum-oxygen octahedron.Classification island chain (single, double) sheet (single, double) frame1. Island silicatesSi:O=1:4Si:O=1:3.5Si:O=1:3Si:O=1:3Si:O=1:3characteristic single: molecular formula: M4+SiO4、 M22+SiO4typ

5、ical 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 silicatessinglecharacteristic 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。singleSi:O=1:3typical minerals pyroxenes，CaMgSi2O6 , Mg2Si2O6doubletyp

6、ical minerals tremolite ; (OH)6Mg6(Si4O11)H2OdoubleSi:O=4:113. Sheet silicatesSi:O=4:10characteristic SiO4以三个以上的顶角相连形成在二维方向呈六角对称的平面无限延伸的层状结构。typical mineralstalcMg3(OH)2Si4O10muscoviteKAl2(OH)2AlSi3O10KaoliniteAl2(OH)4Si2O64. Frame silicatesSi:O=1:2cristobalite typical minerals cristobalite（silica S

7、iO2）, feldsparcharacteristic 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 SummaryTypesFeaturesStructuresSi:OExamples1Island SiO4四面体及其硅氧团之间不共顶点相连，而是通过其余金属离子相连，硅氧团被金属离子隔开形成孤立的岛状。1:4锆英石镁橄榄石石榴石钇铝石榴石 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1:3.51:31:31:3TypesFeaturesStructuresSi:OExamples2Chain 硅氧

8、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。1:34:11辉石角内石3Sheet SiO4以三个以上的顶角相连形成在二维方向呈六角对称的平面无限延伸的层状结构。4:10高岭石云母4Frame 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。 1:2石英长石沸石.Terminology: components , composition and its description , phase , structure.Classification:solid solutioncompounds(intermediate phase)substitutional interstitial primary or terminal ( it must be disordered )intermediate or secondary ordered disordered normal valence electron size ionic : Paulings ruledisordered : (8-N) ruleinterstitial topo