Non-equilibrium melting of colloidal crystals in confinement

Abstract

A novel and flexible experiment is reported for investigation of the non-equilibrium melting behaviour of model crystals made from charged colloidal spheres. In a slit geometry, polycrystalline material formed in a low salt region is driven by hydrostatic pressure up an evolving gradient in salt concentration and melts at large salt concentration. Depending on particle and initial salt concentration, driving velocity and the local salt concentration, complex morphologic evolution is observed. Crystal–melt interface positions and the melting velocity are obtained quantitatively from time-resolved Bragg and polarisation microscopic measurements. A simple theoretical model predicts the interface to first advance, then for balanced drift and melting velocities to become stationary at a salt concentration larger than the equilibrium melting concentration. It also describes the relaxation of the interface to its equilibrium position in a stationary gradient after stopping the drive in different manners. The influence of the gradient strength on the resulting interface morphology and a shear-induced morphologic transition from polycrystalline to oriented single crystalline material before melting are discussed.

Keywords:

• confinement
• zone melting
• colloidal crystal
• colloid
• melting
• microscopy
• phase transition

View correction statement:

Corrigendum

Acknowledgements

We thank S. van Teeffelen and Erdal C. Oguz and Nina Lorenz for helpful discussions and BASF, Ludwigshafen for the kind gift of particles. We gratefully acknowledge financial support by the DFG (SPP 1120, SPP 1296, Pa459/12 and SFB TR6).

Notes

Notes

1. It is still unclear whether in the solid–fluid coexistence region there is steady-state interfacial growth; see, for example, the discussions in 31 and the experimental findings of 42.

2. A different mapping procedure was used by M.S. Ripoll, C.F. Tejero and M. Baus 38.