Recrystallization dissolution

If a glove box is not available, Schlenk-type glassware used with medium vacuum and inert gas is a relatively inexpensive and convenient approach. The use of this glassware is described in a general reference.27 Dissolution, recrystallization, solution transfer, and other simple operations can be carried out on the benchtop. Syringe techniques using apparatus closed with rubber septa also have been developed.28... 

In nonreactive molten salts, on the other hand, flux components are not incorporated into the product phase. Here, the molten salt acts more in the classical sense as a reagent to promote the reaction at a lower temperature than would be required by the ceramic, or direct, route (Section 5.2). This is accomplished by two attributes of molten salts an acid-base equilibrium that enables the general dissolution-recrystallization of metal oxides and a highly electropositive (oxidizing) environment that stabilizes the highest oxidation state of many transition metals (Gopalakrishnan, 1995), which can lead to mixed valency. A plethora of complex transition metal oxides have been synthesized in nonreactive molten alkali metal hydroxides, carbonates, and hypochlorites. Examples of such molten salt routes to mixed transition metal oxides include (Rao and Raveau, 1998) ... 

Gel dissolution Zeolite nucleation Crystal growth of the zeolite nuclei Dissolution/recrystallization of metastable phases (Oswald s Law of successive transformations)... 

Solvothermal reactions in alcohols are sometimes called alcohothermal reactions this word is derived from alcoholysis based on the similarity between hydrothermal and hydrolysis. Alcohols are the most common solvents for sol-gel synthesis. Primary alcohols are fairly stable at higher temperatures (up to 360°C) and therefore are widely used for the solvothermal reactions." For example, amorphous gel derived by hydrolysis of metal alkoxides can be crystallized by solvothermal treatment in alcohols. Since lower alcohols (methanol, ethanol, and 1-propanol) are completely miscible with water, water molecules present in the precursor gel may be replaced with the solvent alcohols. Therefore the precursor gel is easily dispersed in the solvent, where crystallization takes place. Detailed mechanisms for the formation of crystals are not yet fully elucidated. Crystallization of metal oxides is usually reported to take place by dissolution-recrystallization mechanisms, but the mechanism seems to depend on the gel structure. Moreover, water molecules dissolved from the gel in the reaction medium may facilitate crystallization of the product. More discussion is given in Section III.D of this chapter. 

Because dissolution of the whole particle is not expected and because one amorphous particle is expected to transform into a crystalline particle, formation of homogeneous precursor gel is essential. On the other hand, if the real dissolution-recrystallization mechanism takes place, synthesis of homogenous gel does not have any meaning, since preferential dissolution of one component may be expected to occur in the solvothermal reaction. 

Terpstra RA, Bermema P, Hartman P, Woensdregt CF, Perdok WG, Senechal ML (1986) F faces of apatite and its morphology Theory and observation. J Cryst Growth 78 468-78 Thirioux L, Baillif P, Ildefonse JP, Touray JC (1990) Surface reactions during fluorapatite dissolution-recrystallization in acid media (hydrochloric and citric acids). Geochim Cosmochim Acta 54 1969-1977... 

The addition of polyelectrolytes with strong inhibition ability [241,242] will stabilize amorphous nanobuilding blocks in the early stage and then stimulate a mesoscale transformation [40] or act as a material depot in a dissolution-recrystallization process. This could be shown in a time resolved study on the CaCOa scale inhibition efficiency of polycarboxylates, where amorphous precursor particles were detected in the initial stages [243]. 

Catalyst particle growth Migration, Ostwald ripening, dissolution/recrystallization T,E ECSA and performance loss... 

Li3P04, whose presence was detected using XRD, would then dissolve and recrystallize to LiFePOa where it would collect on the edges of the pre-existing LiFePOa nanoplates. Thus, is can be surmised that dumbbell LiFeP04 mesocrystal formation is based on a dissolution-recrystallization process with eventually complete phase transformation. 

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