Aerogel

Challenge

What is aerogel?

Supplies

• • 1 Block of aerogel in protective case

  • 1 Piece of broken aerogel block

What to do

• 1. Hold up the full bock of aerogel and ask visitors what they think it is

  2. Describe its properties and some of its uses

  3. Have visitors hold their hand out flat, palm up

  4. Delicately place a broken piece of aerogel in their palm

  5. Take the piece back and pass it to the next person. Do not let the visitor pick it up, they will crush it.

Inquiry Questions

• • Where would this material be useful?

  • Which of its properties do you think is most important? Why?

  • How might you improve this material?

What’s happening?

Aerogel is a man-made material. It starts as a gel and has the liquid within the gel replaced by gas. This leaves behind the solid matrix of the gel creating a porous material that is extremely lightweight. Replacing the liquid with a gas is a challenging task. There are several ways to do it, but one of the most common is by supercritical drying. To do this, the gel is placed in a container and the pressure and temperature are increased. With enough pressure, liquids and gases act the same and there is no longer a phase change required to go from one to the other. The container is then slowly cooled and the pressure released, making sure to keep the gel below the point where liquid would reform. As a result, the liquid is replaced with gas without using evaporation which would have caused damage to the solid matrix within the gel.

Properties

Aerogels are:

• • the lightest solid material known

  • composed of 99.8% air

  • extremely thermally insulative

  • slightly blue for the same reason the sky is blue (Rayleigh scattering)

Uses

Aerogels are used for:

• • insulation of buildings, skylights and space probes

  • trapping space dust on the NASA Stardust mission

  • adsorber for cleaning up spills