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SUMMARY:Coarsening and grain boundary dynamics in a two-dimensional colloi
 dal hard sphere system - Roel Dullens\, Chemistry\, Oxford
DTSTART:20140522T103000Z
DTEND:20140522T113000Z
UID:TALK51601@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Understanding grain growth in polycrystalline materials is cru
 cial in metallurgy to enable tuning the mechanical properties of metals an
 d alloys. Also from a fundamental point of view it is interesting to study
  grain growth dynamics as a non-equilibrium ordering process [1]. From an 
 experimental point of view\, colloidal polycrystalline materials are very 
 convenient model systems to study grain growth\, since they can be imaged 
 by means of simple optical microscopy at single particle resolution and hi
 gh frame rate [2]. This enables bridging the time and length scales betwee
 n the single particle and grain size level and obtain a comprehensive stru
 ctural and dynamical picture of grain growth in a single experiment.\n\nIn
  this work we develop a two-dimensional colloidal hard sphere system and c
 haracterise its equilibrium structure by comparing the radial distribution
  functions and experimentally determined contact values to a recent fundam
 ental measure theory for hard disks [2]. This system is then used to study
  the grain growth process of a polycrystalline monolayer of colloidal hard
  spheres after a quench into the crystalline state. The time-evolution of 
 the orientational order is studied and we find strong orientational orderi
 ng. The orientational correlation function exhibits dynamic scaling [3] an
 d the associated correlation length increases as a power law in time\, whe
 re the exponent is lower than expected for an isotropic curvature driven g
 rowth [4]. We find that the annihilation of large angle grain boundaries i
 s the main coarsening mechanism\, which is supported by the linear decay i
 n the orientational correlation function at intermediate distances [1\, 4]
 . We finally show that the migration of large angle grain boundaries is ca
 used by small and local particle displacements\, thereby gradually changin
 g their local orientation. Interestingly\, the displacements are found to 
 correspond to the minimum displacement vectors obtained by geometrically m
 apping the expanding grain onto the shrinking grain.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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