Temperature ripening

Age of Ripening temperature Ripening temperature Ripening temperature... 

The final factor known to influence the rate of ripening and cheese quality is ripening temperature. Ripening at elevated temperatures is normally... 

Pang, Y. and Bao, X. (2003) Influence of temperature, ripening time and caldnation on the morphology and crystallinity of hydroxyapatite nanoparticles. Journal of the European Ceramic Society, 23,1597-704. 

There aie a number of major indusuial problems in the operation of the steam reforming of metlrane. These include the formation of carbon on the surface of the catalyst, the sulphidation of the catalyst by the H2S impurity in commercial natural gas, and die decline of catalytic activity due to Ostwald ripening of the supported catalyst particles by migration of catalyst atoms from the smaller to tire larger particles, as the temperamre is increased. A consideration of tire thermodynamics of the principal reaction alone would suggest that the reaction shifts more favourably to the completion of the reaction as the temperature is increased. 

S. Olive, U. Grafe, I. Steinbach. The modelling of Ostwald-ripening during non-isothermal heat treatments resulting in temperature dependent matrix solubihty of the precipitate forming elements a further development of the LSW-theory. Comput Mater Sci 7. 94, 1996. 

Fig. 5. Size and density of Ni nanocrystals as a function of (a) initial Ni film thickness and (b) annealing temperature (inset shows the AFM micrograph of Oswalt ripening at high temperatures).

There is an upper limit of about 23 microns in size. This may be due to the fact that the precipitation was accomplished at 90 C., or from the fact that rare earth oxalates tend to form very small particles during precipitation which then grow via Ostwald ripening and agglomeration to form larger ones. Nevertheless, it is clearly evident that when the oxalate is heated at elevated temperature ( 900 °C), the oxide produced retains the same PSD characteristics of the original precipitate. 

TBP and injected into a hot ( 350 °C) solution of TOPO (12 g). The injection of CdSe precursors into the hot solution ofTOPO resulted in spontaneous nucleation of CdSe nanocrystals and a decrease in temperature. Once the temperature was stabilized, an additional amount (0.4 mL) of the precursor solution was added for the growth of the nucleated nanocrystals. Here, Ostwald ripening was avoided by separating the nucleation and growth processes. All the reagents and the reaction were kept under an Ar atmosphere to avoid fire hazard and surface oxidation of the nanocrystals. 

Figure 6. TEM micrographs representing the transformations of (a) polydispersed nanoparticles upon (b) alkanethiol addition at room temperature and (c) after digestive ripening (inverse micelle system). (Reprinted with permission from Ref [49], 2002 American Chemical Society.)...

Thus, we see that the digestive ripening process leads to highly monodispersed nanoparticles that can come together to form ordered superstructures similar to atoms or molecules that form crystals from a supersaturated solution. Then if the superstructure formation can indeed be related to atomic/molecular crystallization, it should also be possible to make these supercrystals more soluble in the solvent with a change of temperature. Indeed, the optical spectra of the three colloids prepared by the different thiols discussed above exhibit only the gold plasmon band at 80 °C suggesting the solubilization of these superlattices at the elevated temperatures [49]. 

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