Aerogel is an advanced man-made silicon
developed in the 1930/40s. Comprising of mainly air
, it has some astounding material properties.
How is it made:
Aerogel is formed from a silica-dioxide gel. If the liquid in the gel is left to evaporate, the gel collapses. However, by using a process known as supercritical drying, the liquid is evaporated without causing the structure of the gel to collapse and the aerogel retains its material properties. The end result is a light translucent material.
Properties of aerogels include:
- Lowest solid density: aerogel is the lightest man-made material with a density only three times that of air
- Highest porosity: This material can be up to 95% porosity with the pore size ranging up to micron size.
- Very high surface area: Aerogels can have up to 1000 square metres of surface area per one gram
- Versatile compositions: Aerogels can be made with a wide range of chemical compositions which allows all these properties to be altered to suit.
In addition, aerogels are non-flammable, non-toxic, lightweight, transparent, and thermally stable to about 650°C.
Uses of Aerogels:
- Absorbents – with their huge surface area, and porus nature, aerogels are able to absorb relatively large amounts of gases/particles
- Catalysts – the large surface area of aerogels allows more reactions to take place making them ideal catalysts
- Insulators – aerogel is thermally stable up to 650 deg C. Refer to the section below on ‘Just how good is aerogel as an insulator?’.
Other uses include: semiconductor
, dielectric, ferroelectric, diffusion
controllers, electric conductors.
Just how good is aerogel as an insulator?:
If the aerogel material is filled with air, it has the same insulation capability as 15 cm (6 inches) of fibreglass batting. If it is evacuated (ie no air in the aerogel), it is the equivalent of 97cm (38 inches) of fibreglass batting.
I remember seeing a memorable picture with a 2.5cm (1 inch) thick slab of aerogel sitting upright on a bench. On the left side was a human finger touching the aerogel slab, on the right side has an oxy-acetylene torch trying to burn the aerogel. The human finger found the aerogel quite comfortable to touch!