e media strikes again! - materials media strikes again! j.w. morris, ... creates 3d network...

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  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    e media strikes again!

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Microstructure

    Crystalline solids Basic crystal structure Defects in crystals

    Amorphous solids; glasses Random distributions of atoms or molecules

    Macromolecular solids Materials built of distinguishable molecules Polymers Silicates Biological membranes

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Amorphous Solids (Glasses)

    Solids with essentially random atomic arrangements

    Configurational glasses atoms or molecules dont fit

    Chemical glasses bonds forbid order

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Amorphous Solids (Glasses)

    Materials with nearly random atom configurations frozen liquids

    Used for: Isotropic properties

    Window glass Microstructural uniformity

    Metallic glass (Metglass) magnetic materials Formability

    Thermoplastics

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Amorphous Solids (Glasses)

    Amorphous structures are never preferred by nature

    Liquid cooled too quickly to crystallize is a glassy solid at T

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Chemical Glasses

    Atoms are bonded into an irregular pattern

    Example: window glass SiO2 Si (+4) bonded to four O (-2) in tetrahedral coordination Creates SiO4-4 tetrahedra Bonded at corners (Si - O - Si) to generate solid SiO2 Bonds tend to create frozen, irregular patter

    = Oxygen

    = Silicon

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Chemical Glasses: Glassformers

    Glass-formers disrupt bonding, inhibit crystallization Ionic species such as Na, Pb, Mg in silica Bond to oxygen, seal tetrahedra

    Glass-formers may also contribute properties Optical clarity of leaded crystal Color of tinted glass (pink panes of Beacon Street)

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Configurational Glasses

    Thermoplastic polymers Long-chain polymers tangle like

    strands of spaghetti

    Metallic glasses Unusual magnetic, chemical or

    mechanical properties Always require glass-formers

    (metalloids, rare earths) Require rapid cooling

    Quenched ribbons or sheets Bulk materials

    Soft magnets (transformers)

    liquid metal (golf clubs) - R. Busch, JOM, 52, 39 (2000)

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Macromolecular Solids

    Polymeric solids Organics Plastics

    Silicates Rocks and minerals Clay

    Fibers Fabrics Fiber composites

    Lipid bilayers Biological membranes

    Quasicrystals

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Chain polymers

    Carbon bonded to H and to itself forms the simplest polymer chain

    C

    H

    H

    HH

    Methane

    H C C H

    H H

    H HEthane

    H C C C H

    H H H

    H H HPropane

    HH C C C

    H H H

    H H H

    ^ ^ ^ C C C

    H H H

    H H HPolyethylene

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Chain polymers

    The chain polymer is elaborated by replacing H with an atom or molecule

    (R) Replacing H by a double bond

    between carbons

    The basic block (mer) multiplies itself into a polymer E.g., by breaking double bond to bond

    blocks into chain

    C C

    H H

    H R

    C C

    F

    F F

    F

    C C

    H

    H

    CH3

    C O

    O CH3Tetraflourethylene (teflon) Methyl methacrylate

    (plexiglass or Lucite)

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Order in Polymers: Sidegroup Order

    C C

    H H

    H R

    C C

    H H

    H R

    C C

    H H

    H R

    C C

    H H

    H R

    C C

    H

    HH

    R

    C C

    H H

    H R

    C C

    H H

    H R

    C C

    H

    HH

    R

    C C

    H

    HH

    R

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    isotactic (one side)

    syndiotactic (alternate side)

    atactic (random)

    Cis-polyisoprene (rubber)

    Trans-polyisoprene (gutta percha)

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Order in Polymers: Copolymers

    random copolymer

    A, B = mers

    regular copolymer

    block copolymer

    branched copolymer

    ...AAABABAABAAAABAB.. ..ABABABABAB..

    AAAAAAAAAABBBBBBAAAAAAAAAABBBBBBAAAAAAAAAA

    AAAAAAAAAAAAAAAAAAAAAAAA

    AAAAAA

    AAAAAAAAAAAAAAAAAABBBBBB

    BBBBBB

    (a)

    (b) (c)

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Order in polymers: Crystallization

    Long-chain polymers crystallize by aligning or folding chains

    Chain polymeric solids are usually only partially crystallized (10-90%)

    fringed micelles folded chain crystals

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Thermoplastic Polymers (Glasses)

    To suppress crystallization: Use long chains, irregular sidegroups to inhibit crystallization Cool quickly to freeze in glassy state

    Stable configurational glasses soften on heating Thermoplastic forming

    v

    T

    liquidglass

    crystal

    Tg mT

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Network Polymers

    Blocks join by bonds to form a three-dimensional network The resulting network polymers are

    Easy to cast into complex shapes Dimensionally stable and strong Thermosetting - decompose rather than soften on heating

    OH

    H

    H

    H

    H

    H

    OH

    H

    H

    H

    H

    H

    O

    C

    H H

    OH

    H

    H

    H

    OH

    H H

    H

    H

    H

    C

    H H

    OH

    H H

    C

    H HC

    H H

    H HC Phenol-formaldehydem(Bakelite): The first blockbuster commercial polymer

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Network Polymers: Crosslinking

    Chain polymers connected by chemical bonds form 3d networks Example: vulcanization of rubber

    Sulpher (S2) bridges cis-ordered groups Cross-linking turns rubber from gum to engineering elastomer The breakthrough that made the automotive industry:

    No rubber tires, no highways, no cars

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH 3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH 3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    HS S

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH 3

    C

    H

    C

    H

    H

    C

    H

    H

    C

    CH 3

    C

    H

    C

    H

    H

    C

    H

    HS-S

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Network Polymers: Elastomers

    Elastomers are kinked polymers that stretch like springs Rubber is kinked by the cis-configuration at the C=C double bond

    They must be cross-linked to provide a reference frame Otherwise chains simply slide over one another For example, natural rubber is a gum Vulcanized rubber is an elastomer: it recovers its shape after a stretch

    S S

    S S

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Macromolecular Solids

    Polymeric solids Organics Plastics

    Silicates Rocks and minerals Clay

    Fibers Fabrics Fiber composites

    Lipid bilayers Biological membranes

    Quasicrystals

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Silicates

    Are the basis for rocks, clays and minerals

    Common dirt is, in fact, aluminosilicate: Si-Al-Fe oxide

    Other minerals also have complex compositions with many elements

    Study SiO2 as a simple prototype

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Silicates

    SiO4-4 tetrahedra join at corners to form networks: strong, hard structure

    Open structure results in several crystal structures, glasses

    Glass formation promoted by ions that terminate oxygen bonds

    M+--- M++

  • J.W. Morris, Jr. University of California, Berkeley

    MSE 200A Fall, 2008

    Layered Silicates: Clay

    If SiO4-4 join at three corners, they form sheets

    In clay, two sheets are bound together by ions to form a sandwich