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Solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern are known as crystalline solids. Metals and ionic compounds typically form ordered, crystalline solids. A crystalline solid has a precise melting temperature because each atom or molecule of the same type is held in place with the same forces or energy. Amorphous solids or non-crystalline solids (or, sometimes, glasses) which lack an ordered internal structure and are randomly arranged. Substances that...
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Theoretical Calculation and Experimental Verification for Dislocation Reduction in Germanium Epitaxial Layers with Semicylindrical Voids on Silicon
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Dislocations in Polymer Crystals.

H D Keith1, Elio Passaglia1

  • 1Bell Telephone Laboratories, Murray Hill, N.J.

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Summary
This summary is machine-generated.

Dislocations play a limited role in plastic deformation of chain-folded polymer crystals due to restricted molecular chain movements. Other mechanisms are likely responsible for significant deformations in these materials.

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Area of Science:

  • Materials Science
  • Polymer Physics
  • Solid Mechanics

Background:

  • Understanding plastic deformation in polymer crystals is crucial for material design.
  • Dislocations are known mechanisms for deformation in crystalline solids.
  • Chain folding in polymers introduces unique structural constraints.

Purpose of the Study:

  • To examine the role of dislocations in chain-folded polymer crystals.
  • To investigate the influence of dislocations on plastic deformation mechanisms.
  • To assess the limitations imposed by molecular structure on dislocation activity.

Main Methods:

  • Theoretical analysis of dislocation movement in polymer crystal structures.
  • Consideration of constraints from primary bond integrity and chain folding.
  • Comparison with deformation mechanisms in n-alkanes and extended chain crystals.

Main Results:

  • Primary bonds in polymer backbone chains remain intact during deformation.
  • Chain folding significantly restricts the types and number of possible dislocations and glide processes.
  • Dislocation mechanisms alone cannot account for substantial plastic deformation in chain-folded polymers.

Conclusions:

  • Deformation in chain-folded polymer crystals is not solely governed by dislocation glide.
  • Alternative or complementary deformation mechanisms are necessary to explain observed plastic behavior.
  • The specific crystal structure, including chain folding, dictates the deformation pathways.