The Sol-gel Method
The process of sol-gel has been investigated intensively and used in recent years. The most important factors affecting its wide application are that the method is relatively easy rather than other processes. It provides a good enhancement for metallic biomaterial coating layers on the substrate. The sol-gel process is a versatile solution method for making nanoparticles. In general, the sol-gel process involves the transition of a system from a liquid ‘sol’ which is mostly a colloidal form converted into a solid ‘gel’ phase. The Block diagram of the sol-gel technique is shown in figure 1.4. An organic compound such as metal alkoxide/inorganic metal salts is used as precursors known as ‘sol’. During the process, the acid or base is added to maintain the pH of the solution.
After converting the solution to a gel, the solvent is removed by centrifugation. With further drying, the gel is converted into powder form after that this powder is kept in the furnace for heat treatment at a convenient temperature to get nanocrystalline powder or nanoparticles. Sol-gel can control the size of particles by variation in the parameters like solution composition, pH, and temperature.
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