Micro-porosity evolution

Microstructure evolution in solids formed from a melt is important in processes such as prilling or casting. For example, in aluminum alloy shape casting the final microstructure depends directly on the as-cast microstructure since the only post-casting process is the heat treatment. The micro-porosity formed owing to the combined effects of the volumetric shrinkage upon the solidification of the melt and the precipitation of the dissolved hydrogen affects the final properties of the aluminum alloy. 

For silica gels a number of parameters have been demonstrated to have a large effect on the evolution of porosity and subsequently on the resulting silica materials [1]. Almost dense, micro- or mesoporous silica materials can be obtained depending on the experimental conditions in which hydrolysis and condensation reactions of silicon alkoxides are carried out. This is not the case for transition metal alkoxides which are very sensitive to hydrolysis. They do not cillow the adaptation of sol-to-gel transition in order to obtain controlled porous textures. Some years ago special attention was paid to the utilization of amphiphilic systems as reactive media to control hydrolysis and condensation kinetics with transition metal alkoxides [37]. In a more recent work Ayral et al. 

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