6.A] What are nanomaterials? Explain the synthesis of nanomaterial by sol-gel process.
Answer:-
The size of the materials at least in any one of its dimensions ranges between 1 to 100 nm is called nanomaterial.
synthesis of nanomaterial by sol-gel process:-
The sol-gel process is shown in the figure, it involves the evolution of networks through the formation of a colloidal suspension (sol) and gelation of the sol to form a network in a continuous liquid phase (gel).
Metal or metalloid element surrounded by various reactive ligands is processed to form a dispersible oxide to form sol in contact with water or dilute acid.
Removal of the liquid from the sol yields the gel. The sol/gel transition controls the particle size and shape.
Sol-gel synthesis may be used to prepare materials with a variety of shapes, such as porous structures, thin fibers, dense powders, and thin films.
Metal alkoxides are used as precursors in sol-gel operation. The metal alkoxides are hydrolyzed in an alcohol solution containing a controlled amount of water.
The sol-gel chemistry can be represented by the following two reactions:
Sol-gel process can be characterized by series of distinct steps:
Step-1:Formation of stable alkoxide solution (the sol)
Step-2:Formation of oxide-or alcohol-bridged network (the gel) by condensation method.
Step-3:Aging of gel by heating until the gel transforms to sloid mass.
Step-4:Drying of gel. (Water and other volatile liquids are removed from the gel network.
Step-5:Dehydration, during this step, M-OH groups are removed, and stabilize gel by rehydration,
Step-6: Heating at high temperature (>8000C). The pores of the gel network are collapsed, remaining organic species are volatilized.