AEROGEL

HISTORICAL ORIGINS

• Aerogel was invented some time between 1930 by Dr Samuel Stephen Kistler

• But actual commercial production was not done till late 1990s .

WHAT IS AEROGEL …?

• Aerogels are a diverse class of porous, solid materials which exhibit an uncanny array of extreme materials properties

• Silica Aerogel• Organic and Carbon Aerogels• Metal Oxide Aerogels• Metal Aerogel

SPECIAL PROPERTIES OF AEROGEL

• extraordinarily strong in compression • highest compressive strength to

weight ratio of any known material• Very high thermal insulation

RECORDS HELD BY AEROGEL

• Lowest density solid (0.0011 g /cm3)• Lowest optical index of refraction

(1.002)• Lowest thermal conductivity (0.016W

/mK)• Lowest speed of sound through a

material (70 m/s)• Lowest dielectric constant from 3-40

GHz (1.008)

MANUFACTURING OF AEROGEL

• Preparation of a hydrogel (gels with water as a solvent) in reaction of sodium silicate with hydrochloric acid.

• Removal of sodium and chlorine ions. This step involves a long and tedious soaking of the gel.

• Converts the hydrogel into alcogel by replacing water with ethyl alcohol in a lengthy process of solvent replacement.

• Drying at above critical conditions for ethyl alcohol. • The balanced chemical equation for the formation of a silica

gel from TEOS is:• Si(OCH2CH3)4 (liq.) + 2H2O (liq.) = SiO2 (solid) + 4HOCH2CH3

(liq.)

SUPERCRITICAL DRYING

• The Critical Point• Surface Tension and Capillary Stress• Shrinkage• Properties of Supercritical Fluids• CH3OH Methanol 239.50C

79.783atm• CO2 Carbon dioxide 31.130C

72.786atm

High-Temperature Supercritical Drying

Most organic solvents have relatively high critical temperatures of 300-600°C with critical pressures of 50-100 atm, and are dangerously flammable and potentially explosive at these conditions.

Low-Temperature Supercritical Drying from Carbon Dioxide (the Hunt

Process)• Instead of using flammable, explosive solvents, a

safer, non-flammable solvent can be used instead–carbon dioxide. In this process, the organic solvent in a gel is replaced with liquid carbon dioxide by soaking. The liquid carbon dioxide can supercritically extracted at a much lower temperature (31.1°C) than an organic

solvent and without the risk of combustion.

APPLICATIONS

• SPACE APPLICATIONS • ELECTRICAL AND ELECTRONIC

APPLICATIONS • ACOUSTICAL AND MECHANICAL

APPLICATIONS  • OPTICAL PROPERTY APPLICATIONS  • OPTICAL PROPERTY APPLICATIONS • THERMAL APPLICATIONS ( Superinsulator)

NASA STARDUST COLLECTOR

THERMAL INSULATION

• Conduction• Convection• Radiation

HIGH STRENGTH TO WEIGHT RATIO

• Low Density • High Compressive Strength

OPTICAL PROPERTIES

Conclusion

• Aerogel will probably be a common household name in the next decade although it is not yet ready for commercial use.

• Eco friendly building design ( replace glass pane)