Aerogels
What is Aerogels
Aerogels are a diverse class of porous, solid materials that
exhibit an uncanny array of extreme materials properties.
Most notably aerogels are known for their extreme low
densities
They are solid to the touch
What is it made of
The term aerogel does not refer to a particular substance, but rather to a geometry including:
Silica
Most of the transition metal oxides (for example, iron oxide)
Most of the lanthanide and actinide metal oxides (for example, praseodymium oxide)
Several main group metal oxides (for example, tin oxide)
Organic polymers (such as resorcinol-formaldehyde, phenol-formaldehyde, polyacrylates, polystyrenes, polyurethanes,
and epoxies)
Biological polymers (such as gelatin, pectin, and agar agar)
Semiconductor nanostructures (such as cadmium selenide quantum dots)
Carbon
Carbon nanotubes
Metals (such as copper and gold)
Production
Aerogel is derived from gels, which are substances in which solid
particles span a liquid medium
Supercritical drying process; performed under intense heat and
pressure that preserve the structure of the gel
1. Pressurize and heat the gel past its critical point -- at high
temperatures, there's no difference between gas and liquids.
2. Depressurize the gel while it still remains above its critical
temperature. As the pressure decreases, molecules are released as a
gas and the fluid grows less dense.
3. Remove the gel from heat source. After the structure cools, there's
too little alcohol to recondense back into liquid, so it reverts to a gas.
4. What's left behind is a solid made of silica, but now filled with gas
(air) where there was once liquid.
Properties
lightweight; It is the lowest-density solid on the planet. Some types are composed of more than 99%
air, yet they still function as solids
extremely high in surface area; It can have a surface area up to 3,000 square meters per gram,
meaning that a cubic inch of aerogel, if flattened out, could cover an entire football field; and
strong; It can support up to 4,000 times its own weight
good thermal insulation.
How it works
The pores are so small, and gas phase heat conduction is very poor
Molecules of air cannot travel through the aerogel, so there is poor heat transfer through
the material
Aerogel insulation can be a great electrical conductor, yet when made from different
materials, it can also be an effective thermal insulator
Applications
The three most common types of aerogels are silica, carbon and metal oxides
Carbon Aerogel Insulation Material
black and feel like charcoal to the touch.
they make up for in high surface area and and
electrically conductive capabilities
useful for supercapacitors, fuel cells, and
desalination systems (the process of turning
salt water into fresh water)
The three most common types of aerogels are silica, carbon and metal oxides
Metal Aerogel Insulation Material
made from metal oxides and are used as
catalysts for chemical transformations
also used in the production of explosives and
carbon nanotubes, and these aerogels can
even be magnetic
Each type of metal oxide results in an aerogel
of a slightly different color
The three most common types of aerogels are silica, carbon and metal oxides
Silica Aerogel Insulation Material
The most common type
blue
The aerogel scatters, or reflects, the shorter wavelengths of light more easily than the longer ones
an ideal choice for applications where light scattering and diffusion is needed, such as in
daylighting units for buildings, architectural tensile roofing, antiglare and antireflective matte
coatings and plastics, light-emitting diode (LED) diffusors, displays and lighting, and more
Hypersonic Inflatable Aerodynamic Decelerator (HIAD)
an inflatable reentry vehicle that is folded and stowed inside a launch vehicle
The HIAD enables larger masses to be carried through the atmosphere more slowly and safely, and it
reduces the heat to which the vehicle is subjected
The HIAD is covered by a Flexible Thermal Protection System, which uses aerogels as an insulator to
protect the payload
The Flexible Thermal Protection Systems use baseline aerogel insulation blankets
Thank
you