AeroGel - The Perfect Home Insulation

An aerogel is a manufactured porous solid consisting almost entirely of gas (air) with a very fine latticework of solid material in a spherical shape. This solid material makes up anywhere from five (5%) to one percent (1%) of the volume of the aerogel. Despite the name aerogels do not contain a gel; though they begin life as a material matrix with liquid (gel) supporting the lattice.

In the past the process of making aerogels has been quite difficult and expensive due to the fact that the gel of each sphere must evaporate without destroying the outer shell it supports. Since evaporation typically causes a surface tension effect that pulls the lattice apart a method to cause the gel to "disappear" without traditional evaporation had to be found. Traditionally this has been done by replacing the gel with acetone and then carbon dioxide at high temperatures and pressures.

Aerogels have been called "solid smoke," "frozen smoke," or "blue smoke" based on their appearance. This appearance is due to the lattice of solid material causing the light that hits it to bounce off in many different directions with successive layers of the lattice.

History
The first aerogel was created to satisfy a bet. The bet was between Samuel Stevens Kistler, professor of chemistry, and Charles Learned. The bet was "to see if they could replace the liquid inside of jelly in a jar without causing any shrinkage." Clearly Kistler won the bet.

For a time Kistler worked for Monsanto Corporation developing aerogels as fillers for paint, but Monsanto eventually abandoned the concept in 1970...probably due to cheaper fillers and the high cost of creating aerogels.

By this time Kistler had returned to teaching by taking a post at the University of Utah. Kistler died in 1975, just before a resurgence in interest in aerogels.

Famous Quote
Dr. Peter Tsou of NASA's Jet Propulsion Laboratory once said;

"you could take a two- or three-bedroom house, insulate it with aerogel, and you could heat the house with a candle. But eventually the house would become too hot."

Aerogels are primarily defined by the substance that makes up the matrix, not the gas between the latticework. Aerogels are therefore categorized by the material that makes up the framework.

Silica (glass) aerogels are the most common type, Because it is the most common it is also the most extensively studied. Silica aerogel is the world's lowest-density solid at 1 mg/cm³ (milligram per cubic centimeter).; The density of air is 1.2 mg/cm³  meaning that air is more dense than the lightest silica aerogel.

To get some idea of a milligram imagine a dollar bill, which weighs a gram, cut up into one thousand pieces. Each piece would weigh a milligram.

Silica is not only a good thermal insulator in aerogels, it also absorbs infrared radiation. Such insulation materials allow light to enter buildings, but trap heat for solar heating.

It is higlhy thermally insulating. It has very low thermal conductivity corresponding to R-values of 14 to 105 for 3.5 inch thick bat depending on the structure. This means that a half-inch thick bat of aerogel has about the same insulating properties of three inches of fiberglass insulation. By comparison, typical fiberglass or celulose wall insulation has an R-Value of 3 for 3.5 inch thickness. Silica aerogel has a melting point of 2,192°F (1,200 °C).

Silica aerogels currently hold fifteen records in the Guinness Book of World Records for material properties, including best insulator and lowest-density solid.

Carbon Aerogels
Have similar properties to silica aerogels except that they can be conductive and are very good at gathering and retaining light generated heat. Carbon aerogels are a primary material of study in supercapacitors.

Other Aerogels
Other aerogels have been created with alumina and agar (seaweed). These gels have slightly different properties than silica and carbon aerogels, but they all have high thermal insulation values. Agar aerogels are not only biodegradable, they are edible.

Areogels have many properties not the least of which are the ability to limit thermal transfer.

Silicon Aerogels are:

• Thermal insulator
  
• Have sound absorption properties
  
• Desiccant (moisture absorption)
• Flameproof
• Water permeable (allows breath-ability)
  

Carbon Aerogel have all of the above properties plus:

• Are electrically conductive
• Can store electrical charge (as a capacitor medium)
  
• Absorb Infrared & visible light

Alumina Aerogel's have all of the Silicon aerogel properties plus:

• Can act as a catalyst

SEAGel have all of the Silicon aerogel properties plus:

• Are biodegradable (edible)
  

Nasa has used aerogels in the Mars rovers to keep them from freezing in the sub-zero temperatures on the surface. Nasa has also used aerogels to trap dust streaming off of a comet in the "Stardust" collector experiment.

Dunlop is developing a tennis racket with aerogel filler. The idea is to create a racket that is very strong and extremely light in weight.

Insulating skylight material encased in Lexan. Because aerogel transmits scattered light there is not a suitable form of aerogel for windows...yet. Cabot makes the "nanogel" material for the skylights.

Laken makes a water-bottle insulated with aerogel.

Polarwrap makes shoe inserts made of sandwiched aerogel.

Aerogem makes jewelry made with aerogel.

Aspen Aerogel^tm makes aerogel blankets that are capable of limiting heat pollution from operating equipment as well as quieting machinery covered in their blankets.

New aerogels are now being manufactured more cheaply and plentifully. One of the original drawbacks of an aerogel was it's fragility. Aerogels of the past, though very efficient at thermal insulation, were also very brittle making them poor candidates for building material.

Lately manufacturers have come up with ways of embedding aerogels in flexible plastic thereby creating sheets or bats of the substance.

In this way manufacturered insulating aerogels are similar to fiber reinforced plastic. Another benefit of these new materials is that they are opaque. They also retain low weight and much easier to work with. Unlike fiberglass bat, aerogel bat does not pose a breathing risk nor does it irritate the skin.

Aerogel bat is still more expensive than equivalent cellulose or fiberglass bat, but the prices are coming down. There are now three manufacturers of aerogel insulation; each listed below.

• Aspen Aerogels (U.S.) creates long continuous bats for home insulation called SpaceLoft
  
• Cabot (U.S.) creates bats for home insulation called Nanogel
• Thermablok(U.S.) creates strip of aerogel for peel-n-stick stud insulation; self-named
  

The author owns no stock nor has been compensated in any way for the contents of this article. None of the companies listed paid the author monetarily, with discounts, or freebies for this write-up.