Ostwald Ripening

Synonyms

Crystal growth

Definition

Ostwald ripening (or disproportionation) is the process of disappearance of small particles or droplets by dissolution and deposition on the larger particles or droplets. The driving force for Ostwald ripening is the difference in solubility between the small and the large particles. The smaller particles (with higher radius of curvature) are more soluble than the larger ones (with lower radius of curvature). With time, the smaller particles or droplets dissolve, and their molecules diffuse in the bulk and become deposited on the larger ones. This results in a shift of the particle or droplet size distribution to larger values. The difference in chemical potential between different sized droplets was given by Lord Kelvin:

$$ \rm S(r) = S(\infty )\exp \left( {\frac{{2 \gamma \rm{{V_m}}}}{{rRT}}} \right) $$

where S(r) is the solubility surrounding a particle or droplet of radius r, S(∞) is the bulk solubility, γ is the interfacial tension (for solid...