Aerogel is composed of individual features only a few nanometers in size, linked in a highly porous dendritic-like structure. This exotic material has many unusual properties, such as uniquely low thermal conductivity, refractive index, and sound speed, in addition to its exceptional ability to capture hypervelocity dust.
Aerogel is made by high temperature and pressure critical point drying of a gel composed of colloidal silica structural units filled with solvents. Over the past several years, aerogel has been made and flight qualified at the Jet Propulsion Laboratory. For volatiles collection each Particle Captured in Aerogel collector medium will be dopped with selected absorbents.
Silica aerogel produced at JPL is a water clear, high purity silica glass-like material that can be made with bulk density approaching the density of air.
It is strong and easily survives launch and space environments. To the touch it may feel sticky, with various consistencies depending on the density of the aerogel.
Here is a descriptive guide to help you imagine touching a silica aerogel:. Silica aerogels feel sticky because of the unreacted silanol Si-OH groups which terminate the skin of their skeletons—the -OH groups make weak hydrogen bonds easily, not unlike Scotch TM tape does, which makes it feel sticky.
As mentioned above, silica aerogels usually contain lots of unreacted silanol Si-OH groups on the surface of their skeletons. The presence of these groups makes silica aerogels very hydrophilic—that is, they readily soak up water upon contact and from vapor in the air.
An initially transparent silica aerogel sitting on a table may become cloudy over the course of months to years because of water vapor working its way in. Touching a silica aerogel may leave a white fingerprint behind. Dunking a silica aerogel under water generally causes the monolith to rapidly and irreversibly shrivel up. This applies to other polar solvents as well.
On the flip side, silica aerogels repel non-polar liquids such as benzene, hexane, and gasoline very effectively. Silica aerogels dried by Hunt Process drying are generally very hydrophilic, unless special steps have been taken to water-proof them as described below. Silica aerogels dried by high-temperature supercritical extraction of methanol, on the other hand, are usually reasonably hydrophobic repel water. This is because at high temperatures methanol reacts with surface silanol groups to form methoxysilanol groups that is, Si-OH becomes Si-OCH 3.
As a result, water and other polar solvents are not drawn into the aerogel as easily. Silica aerogels are particularly easy to functionalize—that is, attach chemicals to the surface of their skeletons—because of all the silanol groups Si-OH on their surfaces. Think of these silanol groups as being molecular electrical outlets that we can plug useful molecular appliances into!
When the gel is dried to make an aerogel, these groups stick around and coat the surface of the skeleton of the resulting aerogel. This is where chemists and materials scientists get to have some fun!
You could replace the silanol groups with a non-polar group, such as trimethylsilyl -Si CH 3 3 , which would make the resulting silica aerogel water-proof! Or you could add a fluorophore, which would make the resulting silica aerogel glow under a UV lamp! All sorts of neat things can be attached to silica aerogels to make useful aerogel materials. One interesting example is the attachment of molecules which fluoresce when exposed to oxygen, resulting in silica aerogel that can act like an oxygen sensor!
Water-proofing aerogels is useful especially when using silica aerogels in an application where they need to be transparent, such as in window insulation or a Cherenkov radiation detector. One chemical used to water-proof silica aerogels is hexamethyldisilazane, a compound used to water-proof other materials, which plants those trimethylsilyl groups mentioned earlier over the surface of the gel.
Silica aerogels are best known for combining high optical transparency with tremendously low thermal conductivity, which can take on values as low as 0. See how silica aerogels size up against other types of aerogels and other materials on the Properties of Aerogels page. Silica aerogels have found a wide array of uses, mostly in high-tech science and engineering, but are beginning to enter the commercial mainstream.
Below are a few examples of where silica aerogels have helped out. Thanks in part to the impressive insulating abilities of silica aerogel, the electronics on the twin Mars Exploration Rovers, Spirit and Opportunity, have managed quite nicely on the Red Planet and have well outlasted their design expectations.
Because of its intricate nanostructure and cellular structure, aerogels are excellent at energy damping—and not only just thermal energy damping but also acoustic, electrical, and impact damping as well. So when Dr. Comets eject a plume of particles and dust which give them their characteristic luminescent tail or coma.
Tsou headed a project called Stardust designed to collect ejected particles from comet Wild 2. Relative to the probe, the impact velocity of the particles ejected from the coma was approximately m s -1 13, mph. Albeit the particles being ejected were on the order of a grain of sand in size, at those velocities such particles pack quite a punch!
Using blocks of a special three-layer gradient density silica aerogel, the Stardust probe was able to safely and softly cushion the impact of these particles to a complete stop, leaving the particles embedded in the aerogel collector for extraction and analysis upon returning to Earth.
In the sci-fi series Star Trek , when a body such as the Starship Enterprise jumps to warp speed, it exceeds the speed of light and releases a brilliant flash of light in what amounts to the optical analog of a sonic boom. It turns out that this can actually happen. The speed at which light travels through a material is different depending on the material, and in some cases, is so low that particles with mass such as an electron can actually move faster through the material than light can.
When this happens, a cone-shaped electromagnetic shockwave of light is emitted along the trajectory of the moving particle, manifested as a sort of an ectoplasmic blue glow. This effect is called Cherenkov radiation, and it is a way to detect high-energy particles in a particle reactor. As a result, specially-functionalized silica aerogel powder and blankets have been proposed for use in oil-spill cleanups, and are being developed commercially for this application.
One of the tantalizing commercial applications of silica aerogel is for use as insulation in transparent windows. In terms of heat management, windows are the lossiest materials in pretty much any building although notably more heat is lost through walls and ceilings than through windows since they represent so much more surface area.
Airglass AB of Sweden has made windows of silica aerogel on a very limited basis. In fact, their workshop windows are insulated with silica aerogel! Cabot Corporation licenses a technology to produce translucent granules of silica ambigel ambiently-dried aerogel. This material has been used in diffuse-lighting skylights in buildings.
Aerogels are a class of extremely lightweight materials that have air suspended in some solid material, in which the ratio of air to solid is extremely high. The usual kind of materials that we see in the "bluish" aerogel is made of silica. Aerogels are very heat-resistant, and are used by scientists in the aerospace industry to make lightweight insulators, or as a material that is used to catch space dust.
A group of jellyfish is sometimes called a bloom or a swarm. An aerogel is a porous, ultralight solid substance in which the liquid component is replaced with gas. Scientists call it refraction. Yes sometimes scientists can have disagreements. The most common use for Aerogel is for thermal insulation. Silica Aerogel has been used to help insulate the Mars Rover and protected all the wiring from the extreme temperatures it faces in outer space.
Scientists call the theory The Big Crunch. The proper spelling is aerogel. It is not specially capitalized at the beginning or in the middle, nor should it contain a hyphen or a space.
The word has been in technical usage since and is not a tradename or proper noun. Common incorrect spellings include "Aerogel', "AeroGel", "aero-gel", "aero gel", and alternative phonetic spellings such as "airojell" and "aerojell". We call these scientists horticulturists.
Sometimes they do, sometimes they don't. Scientists usually go to conferences, not camps. Aerogel Solid Smoke. Samuel Stephens Kistler. They call them squints. Log in. Study now. See Answer. Best Answer. Study guides. Science 20 cards. Who is known as the first African American scientist.
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