Competition between heterogeneous and homogeneous nucleation near a flat wall

Area of Science:

• Colloid science
• Materials science
• Crystallization dynamics

Background:

• Understanding crystallization in colloidal suspensions is crucial for materials design.
• Heterogeneous nucleation at surfaces can differ significantly from homogeneous bulk nucleation.
• Charged colloidal spheres offer a model system to study nucleation phenomena.

Purpose of the Study:

• To investigate the competition between heterogeneous and homogeneous nucleation in charged colloidal spheres.
• To analyze crystallization kinetics near container walls versus in the bulk.
• To compare nucleation rates under different particle concentrations.

Main Methods:

• Studied aqueous suspensions of charged colloidal spheres.
• Induced crystallization by shear-melting and subsequent cessation of shear.
• Employed time-resolved static light scattering for low particle densities.
• Utilized ultra-small-angle X-ray scattering for high particle concentrations.

Main Results:

• Observed delayed heterogeneous nucleation at container walls compared to homogeneous bulk nucleation.
• Found that heterogeneous nucleation rate density is slightly smaller than homogeneous nucleation.
• Demonstrated unexpected behavior in the crystallization process near surfaces.

Conclusions:

• Heterogeneous nucleation at container walls is not always faster than homogeneous bulk nucleation.
• The crystallization process in colloidal suspensions near walls is complex.
• Surface interactions significantly influence nucleation kinetics.