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Aerogel is the lightest solid with unique properties: Here’s the science behind it

Ever thought a bet between two colleagues could lead to the creation of the world’s lightest solid which had varying applications? Well, that is exactly what happened when Samuel Stephens Kistler and Charles Learned contested over which one of them could get gas to replace the liquid in jelly without any shrinkage.

The contest in question here gave us what we have come to know as Aerogel, the lightest solid known to man.

Now the term Aerogel comes from the base components required to make it — air and gel. This material is formed when the liquid present in a gelatinous substance is replaced by air, essentially leaving us with the solid shell of the jelly with air filled inside.

The material perplexes most people because of its unique nature, it is solid yet delicate and is porous in nature but it can be modified to do so many things. Aerogel maintains the structural properties of a solid while being 97% air which is the reason for its low density.

The most common form of Aerogel that we come in contact with is silica based. Apart from the basic properties that we know about Aerogel are as follows:

  • Its basic composition is 97% air and 3% solid
  • It’s porous in nature,
  • It’s not dense
  • It has a low tensile strength
  • It has a striking point and an insulating nature

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The science behind it

The basis of the bet mentioned earlier was to replace the liquid present with air without any overall shrinkage in the jelly. Basic science principle state that when a liquid is evaporated out of the jelly, there is a pull on all the molecules present, which causes the structure to shrink and crumple up, in some cases this also leads to breakage of the dried up jelly. So how did Kistler get over this predicament?

What is Aerogel? The science behind it and applications
According to NASA, Aerogel is used on the STARDUST spacecraft to capture comet particles from Comet Wild 2. | Source: Nasa via Wikimedia Commons

Kistler made use of supercritical drying to remove all liquid present. He had learnt that the collapse would occur during traditional evaporation and to counter this he replaced the liquid (water) with alcohol. When he converted the alcohol to its supercritical stage he was able to act upon its unique state of being between a gas and a liquid and make it evaporate, leaving him with the ‘husk’ of the jelly and what came to be known as aerogel.

Applications

Now, Aerogel can also be converted into several other forms of products to provide a wide array of features. Silica Aerogel particles can be mixed with a non-flammable binder to make a paste that can act as an insulator and protect an object from being burnt, this can also be used to make an object waterproof by coating it with Aerogel particles. These applications can be seen in Veritasium’s video about unique things that Aerogel can do.

The above-mentioned applications are just some of the unique features, the one property that is already in use is Aerogel’s insulation. This is possible due to the Knudson effect taking place because of its structure, which prevents the direct flow of air to the base surface that is coated.

Nasa’s Mars Rover used a coating to protect its electronics from damage from the cold weather that it would encounter. Aerogel is now also being converted into a form of cotton for use in clothing and is slowly being adopted for insulation in construction.

Also read: 7 ISRO space missions to watch out for in the future

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