AC LEC 09-09

AC LEC 09-09 - Lecture 9 - Ceramic Materials Ionic-Covalent...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 9 - Ceramic Materials Ionic-Covalent Bonding Crystal Structures NaCl, CsCl, CaF 2 , Al 2 O 3 , graphite, SiO 2 Unit Cell Calculations ionic packing factor volume, planar, linear ionic density Glasses Noncrystalline Materials
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Ceramic Materials GENERAL CHARACTERISTICS High Melting Point High Strength Low Ductility (Brittle) High Chemical Stability Good electrical insulators Good thermal insulators Ionic AND/OR Covalent Bonds TWO TYPES Traditional: Bricks, Glass, Sanitary Ware, tiles; e.g., Clay, Silica, Feldspar Engineered Ceramics: Cutting tools, metal processing, IC Substrates; e.g., Al 2 O 3 , AlN, SiC, Si 3 N 4 CRYSTALLINITY PERFECT LRO (METALS) NO LRO (PVC) LOCALIZED LRO (PE)
Background image of page 2
Basis of Structure in Ceramics Most ceramics have some degree of ionic bonding The packing of ions is a function of two factors: Relative Ion Size Charge Neutrality Coordination Number: Number of Anions surrounding small Cation Condition: Anions MUST touch Cation !!! Radius Ratio: R cat / R an Critical Radius Ratio: Anions touching each other AND the Cation High Radius Ratio implies high Coordination Number
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Packing Cations and Anions ANION CATION STABLE UNSTABLE
Background image of page 4
Radius Ratio: Limiting Case r/R = 0.155 R r
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Coordination Number and Radius Ratios 8 CN 6 4 3 r/R
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/27/2009 for the course MSE 150 taught by Professor Wittig during the Spring '07 term at Vanderbilt.

Page1 / 43

AC LEC 09-09 - Lecture 9 - Ceramic Materials Ionic-Covalent...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online