Ostwald ripening is an observed phenomenon in solid solutions which describes the evolution of an inhomogenous structure over time. When a phase precipitates out of a solid, energetic factors will drive some precipitates to grow, drawing from the others, which shrink. If this process continues, eventually fewer and larger crystals form inside the solid that have smaller and smaller surface-to-volume ratios compared to the smaller particles, thus reducing the energy of the entire system.

The phenomenon was first described by Wilhelm Ostwald in 1896.^[1] Friedrich Wilhelm Ostwald (commonly just Wilhelm Ostwald) (September 2, 1853 - April 4, 1932) was a German chemist. ...

In geology, it is the textural coarsening, ageing or growth of phenocrysts and crystals in solid rock which is below the solidus temperature. It is often ascribed as a process in the formation of orthoclase megacrysts, as an alternative to the physical processes governing crystal growth from nucleation and growth rate thermochemical limitations. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ... In chemistry, materials science, and physics, the solidus is a line on a phase diagram below which a given substance is stable in the solid phase. ... Orthoclase (KAlSi3O8) is an important tectosilicate mineral, which forms igneous rock. ... Bubbles in a soft drink each nucleate independently, responding to a decrease in pressure. ...

In oil-in-water emulsion-type polymerizations, Ostwald ripening is the diffusion of monomer from smaller to larger droplets due to the greater solubility of the single monomer molecules in the larger monomer droplets. The rate of this diffusion process is linked to the solubility of the monomer in the continuous (water) phase of the emulsion. Ostwald ripening is a key mechanism in the destabilization of emulsions (for example, by creaming and sedimentation). An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... This article or section does not cite any references or sources. ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ...

An everyday example of Ostwald ripening is the recrystallization of water within ice cream which gives old ice cream a gritty, crunchy texture. The larger ice crystals grow competitively with the smaller within the ice cream, thereby destabilizing the homogeneity of the emulsion.

In chemistry, the term refers to the growth of larger crystals from those of smaller size which have a higher solubility than the larger ones. In the process, many small crystals formed initially slowly disappear, except for a few that grow larger, at the expense of the small crystals. The smaller crystals act as fuel for the growth of bigger crystals. The process of Ostwald Ripening is fundamental in modern technology for the solution synthesis of quantum dots. Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ...

This spontaneous process occurs because larger particles are more energetically favored than smaller particles. While the formation of many small particles is kinetically favored, (i.e. they nucleate more easily) large particles are thermodynamically favored. This is because small particles have a larger surface area to volume ratio than large particles and are consequently easier to produce. Molecules on the surface are energetically less stable than the ones already well ordered and packed in the interior. Large particles, with their greater volume to surface area ratio, therefore represent a lower energy state. Hence, many small particles will attain a lower energy state if transformed into large particles and this is what we see in Ostwald ripening.

See also

• Rock microstructure
• Kirkendall effect