Preparation of Colloidal Sols and Gels Objective

Colloidal suspensions are used to generate polymers or particles from which ceramic materials can be made by the sol-gel process. The precursors for preparation of a colloidal suspension consist of a metal element surrounded by various ligands (attached groups not including another metal). For example, common precursors for sol-gel synthesis of aluminum oxide include inorganic salts such as Al(NO3)3 and organic compounds such as Al(OC4H9)3. The latter is an alkoxide, the class of precursors most widely used in sol-gel research. Metal alkoxides are popular precursors in sol-gel because they react readily with water. The reaction is called hydrolysis, because a hydroxyl ion becomes attached to the metal atom as follows: