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

Surface Tension and Capillary Stress Shrinkage 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)