Alternative TV screens from liquid cement

Materials World magazine
,
1 Jul 2013

A team of US, Japanese, German and Finnish scientists has figured out the formula for a liquid cement material that could be ideal in flatscreen television displays.

Japanese researchers discovered this new form of material in 2011, but the exact details of how the exciting blend of properties works and how to replicate it were unclear until a new study was released by the collaborative research team, which includes the Argonne National Laboratory in Illinois, USA.

The researchers studied mayenite – a mixture of calcium oxide and aluminium oxide, which is a major component of cement. Through a process of containerless heating, melting and cooling in a controlled atmosphere, the cement can be turned into a glassy state that can trap electrons for electronic conduction.

According to Argonne researcher Rick Weber, the material offers a combination of conductivity and optical transparency that cannot be achieved in a metal, and enables the creation of a composite device that blends the qualities of a semiconductor and an insulator. This combination makes the material useful for thin films, protective coatings, and liquid crystal displays in computers and TVs.

He says, ‘When that composition is treated in the right way – [in] chemically reducing conditions – it can trap electrons in the structure and becomes an electronic conductor. It actually has electrical properties very similar to a metal.’

To prove the unique properties of the material, Weber and his colleagues have adopted a multifaceted approach. ‘We combine high-energy synchrotron X-rays to get very fast measurements, levitation melting to access a super-cooled liquid and a supercomputer to enable modelling of the structure. The supercomputing and high-energy X-rays together are what give us the ability to learn a lot about the structure of the material.’

The aerodynamic levitator allows the team to keep the hot liquid from touching the container sides and forming crystals. The liquid then cools to trap electrons for electronic conduction. The metallic glass-like material also boasts other useful properties. It is less brittle than traditional glass, more corrosion-resistant than traditional metals and potentially cheap to fabricate.

Weber notes, ‘Lime and alumina are very abundant and inexpensive. The price, as with many device materials where one needs high-purity special fabrication techniques, would be relatively high on a per kilogramme basis, but the amount of material used in the device is relatively small.’

Having developed a model that shows the conditions needed to create trapped electrons, the team will test other materials to see if it can make them conduct electricity in the same way.