synthesized from chemical methods, but at the same time it offers the possibility of chemical control over the molecule-to-material transformation process.

The main advantages of sol-gel processing are easy control over the microstructure of the material from the earliest stages of the processing, higher purity, low or high porosity, and greater homogeneity. In addition, it allows facile synthesis of homogeneously doped systems, biphasic nanocom-posites [337, 338]. In terms of economic potential, net-shape casting, extrusion, and coatings on large and complex surfaces are the major engineering advantages [194]. On the other hand, the long processing times, costs of the precursors, large shrinkage, production of volatiles, and fragmentation of the green body due to internal stresses are some of the limitations associated with this technique.

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