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Solid Smoke
By Linda | November 21, 2008
While killing some time before a star show at the Science Center recently, I saw something very interesting at the space exhibit. When I spotted it, I thought it was a hologram. I later learned that people often describe it that way. What it turned out to be was a really remarkable substance called an aerogel, also nicknamed solid smoke, blue smoke or frozen smoke.
The reason an aerogel looks so much like it isn’t really there is that in actuality there isn’t much there. Silica aerogel is an extemely low-density material derived from silicon based gel, in which the liquid component of the gel has been replaced with gas. In fact this material is 99.8% air! There are various types of aerogels including carbon aerogel , alumina aerogel, and even an agar-based aerogel known as SEAgel. Silica aerogel is the most common type of aerogel and the most extensively studied and used.
Although areogels possesses various properties that make them suitable for many industrial uses, the particular quality that landed a specimen in the space exhibit is its exceptional ability to capture fast moving dust - stardust, to be exact! Several space missions including the Mars Pathfinder and the Stardust Space Craft use aerogel to collect and hold interstellar dust for scientific study and analysis. The CAPS (Centre for Astrophysics and Planetary Science) website has more information and images about aerogel and space dust at THIS LINK.
From looking at the specimen in the case, I had the impression that if I were to touch it, it would yield and not have any resistence to pressure. I even imagined that it might feel “gummy” and slightly damp. My impressions were quite wrong.
In actuality, aerogels feel like a light but rigid foam, something between styrofoam and the green floral foam used for arranging flowers. Despite what their name may suggest, aerogels are dry materials and do not resemble a gel in their physical properties. The name comes from the fact that they are derived from gels. Pressing softly on an aerogel typically does not leave a mark; pressing more firmly will leave a permanent dimple. Pressing firmly enough will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass - a property known as friability. Despite the fact that the material is prone to shattering, aerogels are very strong structurally, possessing impressive load bearing abilities
Some more interesting facts about silica aerogel:
- Possesses 39 times the insulation factor of the best fiberglass insulating materials
- Is a powerful dessicant - absorbs moisture from materials it comes in contact with
- Is 1000 times less dense than glass (to which it is structurally related)
- Strongly absorbs infrared radiation
- Is the world’s lowest density solid
- Can support 4000 times its weight in applied force
Want to see & feel the real thing? You can buy a sample of aerogel at United Nuclear. A small chunk or a vial of fragments will cost you $45.00
Topics: Technology, The Cosmos, The Petri Dish |
