Materials

A couple of stories about interesting, new materials caught my eye and I thought I might pass them along.

The lightest solid

In the picture above a 2.5kg brick is supported by 2gm worth of aerogel. Aerogel, which is formed by a process somewhat similar to freeze-drying by removing the water from silica gel and replacing it with gas, in this case probably carbon dioxide, has been around since the 1930’s. It was first produced to settle a bet. The original version of the substance was too brittle to be useful for much but developments in its production have resulted in a product which is not only extremely light (1,000 times less dense than glass) but very strong and resistant to heat and cold.

Applications that have been suggested include use as a building material which would be resistant to fire or blast, as armor, and for use in sporting equipment. Its absortion properties would make it useful to mop up oil or other toxic spills.

Aerogel is also being tested for future bombproof housing and armour for military vehicles. In the laboratory, a metal plate coated in 6mm of aerogel was left almost unscathed by a direct dynamite blast.

It also has green credentials. Aerogel is described by scientists as the “ultimate sponge”, with millions of tiny pores on its surface making it ideal for absorbing pollutants in water.

Kanatzidis has created a new version of aerogel designed to mop up lead and mercury from water. Other versions are designed to absorb oil spills.

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Scientists say that because it has so many millions of pores and ridges, if one cubic centimetre of aerogel were unravelled it would fill an area the size of a football field.

Its nano-sized pores can not only collect pollutants like a sponge but they also act as air pockets.

Researchers believe that some versions of aerogel which are made from platinum can be used to speed up the production of hydrogen. As a result, aerogel can be used to make hydrogen-based fuels.

Aerogel was used in the NASA/JPL Stardust mission to collect cometary particles and interstellar dust.

I wonder if it might have aerospace or automotive applications, too. Can you imagine an aircraft made of translucent, smoky, aerogel? Shades of Wonder Woman’s invisible plane!

The thinnest solid

Graphene is a new material—a gauze of carbon atoms just one atom thick:

Measuring less than 50 atoms wide and one atom thick, Andre Geim’s graphene transistor may represent the best hope yet for delaying the expiration of Moore’s Law. “Silicon will run out of steam in about 20 years,” predicts Geim, a professor of condensed matter physics at England’s University of Manchester. “We have to meet the challenge of keeping up with Moore’s Law.”

A little over two years ago, Geim and fellow University of Manchester professor Kostya Novoselov discovered a new material class: a two-dimensional crystal, representing a single sheet of atoms. The material, graphene, is a gauze of carbon atoms resembling chicken wire and has become one of the hottest areas in physics research.

“Until our discovery, this chicken wire was presumed not to exist in the real world,” Geim says.

The Manchester team reported the first graphene-based transistor at the same time as its materials discovery. The new transistor is a two-dimensional giant molecule that’s still only as thick as a single atom. Other researchers have since reproduced the team’s result, but these first-generation graphene transistors were very “leaky,” meaning their electrical flow could not be switched off to zero.

This limitation restricted the devices’ potential use in high-density electronic circuits. But earlier this year, Geim and his team announced they had worked their way around the problem and can now produce graphene transistors that suit use in microprocessors and other chips.