Thursday, 6 December 2012

AeroGel - WFP Material Potential

Aerogel (also called 'frozen smoke' because of its hazy blue appearance), is a truly remarkable material. It is the lightest and lowest-density solid known to exist.
Do you remember this blog? I think Aerogel may have an edge! Being the world's lightest known solid, it weighs only three times that of air. Combined with a carbon fiber lattice & investment, I can see water fed poles getting lighter & higher. Already Dunlop has incorporated aerogel into the mold of its new series of tennis racquets, and has previously used it in squash racquets. The high aspect ratio of fibers such as fiberglass have been used to reinforce aerogel composites with significantly improved mechanical properties. This futuristic material may just be a leap in the direction of making all wfp's lighter & easier to control & if you feel up to it - you can just make your own. Just don't go out working in a strong wind!

A Solid That's Light as Air: Scientists at the Jet Propulsion Laboratory focused on aerogel -- an extremely lightweight, porous material that is chemically identical to glass, but weighs only a little more than air. Aerogel is the lightest solid known to science. It's also one of the most insulating materials on Earth, the most porous, and it's nearly transparent. Holding a piece of aerogel is an uncanny experience. It's so light it feels nearly weightless, like a chunk of solidified fog or smoke. It feels a bit like Styrofoam, and it squeaks when you rub your finger on it. It's strong enough to support many times its own weight if the load is distributed evenly. But bend it or squeeze it too hard, as one Wired News editor discovered, and a chunk of aerogel will shatter into tiny fragments.

Aerogel-impregnated fabrics from Aspen Aerogels are flexible enough to be rolled up or incorporated into clothing.
Back on Earth, that porousness (aerogel can be up to 99-percent air) makes aerogel an ideal thermal insulator. So it's no surprise that companies are investigating commercial uses for this material, ranging from windows to home insulation to clothing. Such a wealth of useful properties makes aerogel interesting not only to rocket scientists, but to entrepreneurs and venture capitalists, who sunk $50 million last year into Aspen Aerogels, a company devoted to commercializing aerogel. "As an insulator, aerogel is two to four times more efficient than anything else out there," said George Gould, the director of research for Aspen Aerogels.

Aspen Aerogels makes economical aerogel textiles by impregnating "blankets" of fabric with silica gel, then pressurizing the impregnated fabric and extracting the now-supercritical liquid. The result is a flexible fabric with aerogel integrated into its matrix. Prices for the material vary, but a typical price is a few dollars per square foot for quarter-inch thick material. When Aspen Aerogel's second factory is completed later this year, Gould said, the company will be able to produce 100 million square feet per year of its aerogel textiles, bringing costs even lower. Aspen's products have been used to to insulate the pipelines used in deep-sea oil drilling operations, in winter jackets by Burton Snowboards and even to make shoe inserts.

The Flower, the Mona Lisa of aerogel pictures, dramatically demonstrates the superinsulating properties of silica aerogel by insulating a delicate, moist flower from the raging heat of a Bunsen burner.
Other commercial producers of Aerogel include Aerogel Composite and a Swedish company, Airglass, which sells aerogel-based insulated windows. The problem these companies face is that, while aerogel is a vastly superior insulator, the alternatives (like fiberglass or plain glass windows) are dirt-cheap. The high pressure needed to create aerogel (around 800 pounds per square inch) means that producing even a tiny amount requires costly lab equipment. You can buy aerogel samples on eBay but they cost around $30 to $50 for small, nickel-sized chunks.

That means aerogel is unlikely to play a major role in construction or clothing unless its makers can bring the price down much further -- or capitalize on its space-age reputation enough to make customers willing to pay extra for cachet. "The costs are not necessarily prohibitive," said Gould. "Relative to something like fiberglass, the costs are certainly greater but a lot of it has to do with capacity."

Aerogel (Wikipedia, the free encyclopedia). Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. The result is a solid with extremely low density and thermal conductivity. It is nicknamed frozen smoke, solid smoke, solid air or blue smoke owing to its translucent nature and the way light scatters in the material; however, it feels like expanded polystyrene (styrofoam) to the touch.

Aerogel was first created by Samuel Stephens Kistler in 1931, as a result of a bet with Charles Learned over who could replace the liquid in "jellies" with gas without causing shrinkage. Aerogels are produced by extracting the liquid component of a gel through supercritical drying. This allows the liquid to be slowly dryed off without causing the solid matrix in the gel to collapse from capillary action, as would happen with conventional evaporation. The first aerogels were produced from silica gels. Kistler's later work involved aerogels based on alumina, chromia and tin dioxide. Carbon aerogels were first developed in the late 1980s.

Peter Tsou with a sample of aerogel at Jet Propulsion Laboratory, California Institute of Technology.
Despite their name, aerogels are solid, rigid, and dry materials and do not resemble a gel in their physical properties; the name comes from the fact that they are derived(composed) from gels. Pressing softly on an aerogel typically does not leave even a minor mark; pressing more firmly will leave a permanent depression. Pressing extremely firmly enough will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass – a property known as friability; although more modern variations do not suffer from this. Despite the fact that it is prone to shattering, it is very strong structurally. Its impressive load bearing abilities are due to the dendritic microstructure, in which spherical particles of average size 2–5 nm are fused together into clusters. These clusters form a three-dimensional highly porous structure of almost fractal chains, with pores just under 100 nm. The average size and density of the pores can be controlled during the manufacturing process.

A 2.5 kg brick is supported by a piece of aerogel with a mass of only 2 grams.
Aerogels are good thermal insulators because they almost nullify the three methods of heat transfer (convection, conduction, and radiation). They are good conductive insulators because they are composed almost entirely from a gas, and gases are very poor heat conductors. Silica aerogel is especially good because silica is also a poor conductor of heat (a metallic aerogel, on the other hand, would be less effective). They are good convective inhibitors because air cannot circulate through the lattice. Owing to its hygroscopic nature, aerogel feels dry and acts as a strong desiccant. Persons handling aerogel for extended periods should wear gloves to prevent the appearance of dry brittle spots on their skin.

The slight color it does have is due to Rayleigh scattering of the shorter wavelengths of visible light by the nanosized dendritic structure. This causes it to appear smoky blue against dark backgrounds and yellowish against bright backgrounds. Aerogels by themselves are hydrophilic, but chemical treatment can make them hydrophobic. If they absorb moisture they usually suffer a structural change, such as contraction, and deteriorate, but degradation can be prevented by making them hydrophobic. Aerogels with hydrophobic interiors are less susceptible to degradation than aerogels with only an outer hydrophobic layer, even if a crack penetrates the surface. Hydrophobic treatment facilitates processing because it allows the use of a water jet cutter.

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