1. Sol-Gel

2.  - Why Sol-Gel..? ApplicationsConventional methods Glass preparation and ceramics High temparature, thermal decomposition, limited materials DSSC(thin TiO 2 films) Cumbersome, non-uniform and high temp. Coatings and thin film applications Accessibility limitations, scaling, costly and energy intensives

3.   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..

4.   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..

5.   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

6.  … consists of hydrolysis and condensation. Hydrolysis: M(OR) x + H 2 O → HO-M(OR) x-1 + R-OH R: -CH 3, -C 2 H 5 etc. M:Si, Al, Ti etc. Sol-Gel synthesis:

7.  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:

8.  Sol-Gel for TEOS TEOS AND WATER TEOS polymerization

9.  Sol-Gel technologies…

10.   Variation of gelation time with PH Factors affecting Sol-Gel

11.   As the temperature increases the gelation time decreases.

12.   Synthesis of ceramics, glass, fibres  Thin films on substrate  Nuclear fuels (UO 2 and ThO 2 )  Aerogels and xerogels  Optical and refractory ceramic fibers  Zeolite synthesis  Powder abrasives  Optical coating, protective coating on plastic, glass, metals  BaTiO 3 electronic material for capacitors Applications…

13.   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:

14. By Sai Charan