lecture 22 - ME 330 Engineering Materials Lecture 22...

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Lecture 22 Ceramic and Polymer Structure Stephen D. Downing Mechanical Science and Engineering © 2001 - 2010 University of Illinois Board of Trustees, All Rights Reserved ME 330 Engineering Materials
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 1 of 43 Schedule Exam 2 Material
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 2 of 43 This Lecture . .. ± Ceramic Structure ± Polymer Structure ± Mer Structure ± Molecular Structure and Shape ± Copolymers
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 3 of 43 Ceramics ± Fine Ceramics (China, etc) ± Structural Ceramics ± Crystalline ± Long range order ± Amorphous ± Short range (atomic ) order ± Glasses ± Fibers ± Refractories ± Abrasives ± Cement ± Inorganic, nonmetallic elements ± Often compounds intermediate between metallic and nonmetallic ± Carbides, oxides, nitrides ± Bonding predominately ionic ± May be partially covalent ± Depends on electronegativities ± Look at separation on Periodic Table ± Properties we like ± Thermal insulator ± Electrical insulator ± Properties that are not so good ± Brittle!
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 4 of 43 Na + Na + Na + Na + Na + Na + Na + Na + Na + Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Cl - Ionic Bonding ± No free electrons poor conductors of heat and electricity ± Diffusion is difficult, must solidify slowly ± Cation : metallic atom ± Positive charge after donating electron(s) ± Anion : nonmetallic atom ± Negative charge after accepting electron(s) ± Criteria for crystal structure: ± Relative charges of cation and anion ± Crystal must be neutral ± Look at chemical formula ± Relative “size” of cation and anion e.g. Na + + Cl - = NaCl Ca 2+ + 2F - = CaF 2
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 5 of 43 Ceramic Crystal Stability stable stable unstable
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 6 of 43 ± Rocksalt (NaCl) ² Interpenetrating FCC ² A coordination # = 6 ² X coordination # = 6 ² Anion packing: FCC ² Also: MgO, LiF, FeO ± Cesium Choride (CsCl) ² A coordination # = 8 ² X coordination # = 8 ² Anion packing: SC ² Similar to BCC, but… ² NOT BCC!! ± Zinc Blende (ZnS) ² A coordination # = 4 ² X coordination # = 4 ² Anion packing: FCC ² Similar to Diamond ² Highly covalent ² Also: ZnTe, SiC Ceramic Crystal Structures AX-type crystal structures: cations (A) = anions (X)
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ME 330 - Lecture 22 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 7 of 43 More Ceramic Crystal Structures A m X p : different numbers of cations and anions A m B n X p : three species, possibly different numbers ± Flourite (CaF 2 ) ² A coordination # = 8 ² X coordination # = 4 ² Similar to CsCl ² Also: UO 2 , PuO 2 ± Perovskite (BaTiO 3 ) ² Two different cations ¾ Ti 4+ (6) ¾ Ba 2+ (12) ² O 2- (6) ² Label the elements
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This note was uploaded on 10/03/2011 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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lecture 22 - ME 330 Engineering Materials Lecture 22...

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