Liquid-Phase Synthesis Method Sol-Gel Technique

The two processes used to prepare nanostructures of bioactive glass are the sol-gel technique and the flame spray synthesis method. The processes are rather different, as one is performed in liquid phase at room temperature, and the other in gas phase at high temperature. An overview of both schemes, and their characteristics, is provided in the following sections. 

Liquid-phase preparation methods use metal-organic precursors which are converted to inorganic materials, either in water or in an organic solvent. The sol-gel process has a long history in the preparation of silicate systems and other oxides. 

Further investigations into the fabrication of bioactive silicate glass nanoparti-des using sol- el have been carried out recently by Hong et al. [13]. 

For some applications, such as in tissue engineering, it is advantageous to use anisotropic structures such as fibers, and for this purpose a combination of the sol-gel and electrospirming techniques is apphed [14]. Additives such as polyvinyl 

Although the sol-gel technique is versatile, it has limitations in terms of the composition and a high residual water or solvent content indeed, in some cases a high-temperature calcination step is required. Sol-gel processing is also relatively time-consuming and, as it is not a continuous process, batch-to-batch variations may occur among the products. 

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