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Aerogel: Uses & Mechanical Properties

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Aerogel is a mysterious and fascinating material with numerous uses. This lesson will explore some of those uses as well as the challenges scientists face while working with aerogel's unique mechanical properties.

What Is Aerogel?

If materials had their own superlatives, aerogel would win 'most interesting', hands down. From its uses, which include collecting comet dust, to its invention, which was based on a bet between two chemists, there is nothing boring about aerogel.

Like its name suggests, aerogel is part gel and part air. Specifically, aerogel refers to a group of low density, solid materials that are extremely porous. Very simply, it's a gel without the liquid portion. The most common type of aerogel is made from silica, but there is also aerogel made from carbon, metal oxides, and other materials. See, not boring!

Aerogel was invented in the 1930s, and as the story goes, chemist Samuel Kistler bet another chemist that a gel gets its properties from its structure rather than its liquid. In an attempt to win the bet, he evaporated the liquid from a gel and replaced it with gas. It took him a while, but eventually the first aerogel was born.

Mechanical Properties

Aerogel is over 99% air and has a ton of fascinating properties. For example, it's an excellent insulator, it has a low density, and it's lightweight. In fact, there is an aerogel that is seven times lighter than air!

Aerogel is an excellent insulator, and can protect this flower from burning
Aerogel flower

And yet, with all of these amazing properties, aerogel has some flaws. The mechanical properties, or the properties associated when pressure and force is applied to a material, aren't as impressive.

For example, silica aerogels can hold thousands of time times their own weight, but that is only the case when the weight is applied carefully and evenly. And since aerogels are really lightweight, they aren't holding much.

Okay, so aerogel isn't perfect. Specifically, it can:

  • be brittle, meaning it shatters easily.
  • have low toughness; it cannot absorb energy without being damaged.
  • have low compressive strength, which means it break when compressed.
  • be friable, meaning it can break apart and crumble easily.

Even though aerogel has a bunch of amazing properties, the mechanical properties deterred people. But not to worry. Some clever scientists worked to create new, flexible, stronger aerogels.

For example, X-Aerogel is aerogel mixed with lightweight polymers. Even though the polymers made the aerogel three times as dense, it also made it 100 times stronger, and thus more usable.

And then there's fiber-reinforced aerogel composite blankets, which were developed by taking aerogel and placing it onto a fibrous mat. This made the aerogel flexible, while allowing it to retain its insulating properties. This technology has a bunch of uses, from foot warming insoles to pipe insulation.

Uses

Speaking of uses, the modifications that made aerogel stronger and more flexible, greatly increased its usefulness. Today aerogels can be found in paints, wetsuits, windows, insulators, cosmetics, armor, aircraft, and even in nuclear weapons. Recently, scientists made aerogels out of metal chalcogenides, which is a material containing a chalcogen element, like tellurium or selenium. These aerogels can glow, and researchers hope to use them to make hydrogen from water and sunlight.

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