Sol-Gel

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Why Sol-Gel..?

Applications Conventional methods

Glass preparation and ceramics

High temparature, thermal decomposition, limited materials

DSSC(thin TiO2 films)

Cumbersome, non-uniform and high temp.

Coatings and thin film applications

Accessibility limitations, scaling, costly and energy intensives

Process in which solid nano particles are

dispersed in a liquid (a sol) and agglomerate together to form a continuous three-dimensional network extending throughout the liquid (a gel)

Involves hydrolysis and poly-condensation

What’s Sol-Gel..

Solid particles (up to few 100 nm) suspended

in liquid phase i.e. Sol

Solid macromolecule (polymer chains) immersed in liquid phase i.e. Gel

Particles in Sol condense in new phase Gel

Sol-Gel..

Precursors: Metal alkoxides and metal chlorides(as they

readily react with water) e.g. TEOS

Colloid contain broad range of solid(or liquid) particles dispersed in various degrees in liquid.

Sedimentation and centrifugation

Drying and firing

…consists of hydrolysis and condensation. Hydrolysis: M(OR)x + H2O → HO-M(OR)x-1 + R-OH R: -CH3, -C2H5 etc. M:Si, Al, Ti etc.

Sol-Gel synthesis:

1. Alcohol condensation:(OR)x-1-MOH + ROM-(OR)x-1 → (RO)x-1-MOM-(OR)x-1 + ROH

2. Water condensation:(OR)x-1-MOH + HOM-(OR)x-1 → (RO)x-1-MOM-(OR)x-1 + HOH

Condensation:

Sol-Gel for TEOS

TEOS AND WATER

TEOS polymerization

Sol-Gel technologies…

Variation of gelation time with PH

Factors affecting Sol-Gel

As the temperature increases the gelation time decreases.

Synthesis of ceramics, glass, fibres Thin films on substrate Nuclear fuels (UO2 and ThO2 ) Aerogels and xerogels Optical and refractory ceramic fibers Zeolite synthesis Powder abrasives Optical coating, protective coating on

plastic, glass, metals BaTiO3 electronic material for capacitors

Applications…

Cheap and low temp. operation Very thin films of metal oxides can be

obtained Uniform distribution of components and

porosity Better alternative approach to conventional

production of glasses Easy dopant addition in ceramics processing Sol gel material can be obtained as bulks, thin

films, (nano) powders

Advantages:

Thank You

By Sai Charan